How much would I give up buying an older PS ? [2019]

I realize this is an old topic from 2019.  But by way of an update for anyone who lands here from web searches, CS2 - 4 are end of life and no longer available.  CS5 - 6 are on life support.  Adobe stopped selling Creative Suite products in Jan 2017.  They are not legally sold by ANY vendor, retailer or in country. 

As @barbara_a7746676 said, Photoshop Elements or Premier Elements (approx $100, no subscription needed) are good options for occasional photo/video editors and hobbyists.  They lack all bells & whistles of pro-level tools but the learning curve is fairly simple.
https://www.adobe.com/products/photoshop-elements.html

Creative Cloud Photography Plan (approx $10/month for 12 months). Includes the following:

• Photoshop CC and Photoshop on iPad
• Lightroom on desktop, mobile and the web
• Lightroom Classic
• Portfolio website + hosting
• Creative Cloud Express (free starter plan)
• Bridge
• 20 GB cloud storage (upgradable to 1 TB).

https://www.adobe.com/creativecloud/photography.html

Premium Creative Cloud Express ($10/month).

• Creative Cloud Express app (web and mobile)
• Premiere Rush (video editing on desktop and mobile)
• Photoshop Express (mobile)
• Spark Video (mobile)
• Spark Page (mobile)
• Adobe Portfolio website + hosting
• 100 GB of cloud storage
• All premium templates and design assets including the entire collection of over 160 million royalty-free Adobe Stock photos.

https://helpx.adobe.com/express/using/express-overview.html

Creative Cloud All Apps (51 + apps & services) and Single Apps Plans
https://www.adobe.com/creativecloud/plans.html

Take a look at Photoshop Elements. It has most of the same features as Photoshop, is much less expensive, and you can get a perpetrual license (no subscription). Elements is an excellent value.

You can download the 30-day trial to try it out. https://www.adobe.com/products/photoshop-elements/free-trial.html

If you can get an older CS version that you know is legal and functional, go ahead and do so. You will save in the long term.

Be aware though, that if you need them some newer functions may not be included in different apps. Illustrator, and InDesign comes to mind where files created in newer versions may not even open in the older apps.

Mangurian, I'm a certified/licensed Web Designer so I do have a need to use PhotoShop, I have been using  CS4 for close to 10 years now. I researched the CS6 & CC upgrades and although there are some new great features... in my opinion...not worth the cost. I can still do 95% of both what the newer versions can do, but may just take more steps. 

Use CS4 & Spend about $10 on Amazon and buy the    CS4 Classroom book...

even after 10 years I still go back & refer to it as needed.  Great Tutorials on a CD included in the book... No Need to rely on Adobe online things... Hope this helps...  PMF Web Design

Old perpetual Photoshop versions have no Adobe support except for installation problems for the OS they are designed for old versions are also Platform dependant.  They run on Windows or Mac OS not on either the code is not the same one both systems.  Make sure you get the version for your Platform.  Also if you are using a MAC apple will stop supporting old 32 bit applications in up coming version of Mac  OS.  You need to get CS5 or CS6  older version for sure will not run on Macs in next release of Mac OS.  Apple new mobile IOS versions also do not support old 32 bit Apps.   To use old Application and Apps you may need to run oldx Operating system versions.

From

Adobe Photoshop version history - Wikipedia

CS5

• Content Aware Fill
• Puppet Warp Tool
• 64 bit for Mac OS X
• Bristle Tips
• Mixer Brush
• Automatic Lens Correction
• Easier HDR toning for beginners
• Improved selection and masking controls
• Camera RAW grain control
• New Blend modes: Subtract and Divide
• GPU HUD controls for brush resize, color picker, color sampling
• Improved Ray Tracing quality and speed (Extended)
• Repousse 3D extrusion tool (Extended)
• Image based lights (Extended)

CS5.1

• Interacts with remote applications over TCP/IP, such as tablets and other computers.
• Subscription model pricing^[10]
• Last release for Windows Vista SP1, SP2, Windows 7 RTM and Mac OS X Leopard on Intel-based Macs

CS6

• Last perpetual license. However, as of January 9, 2017, Creative Suite (CS6 or earlier) perpetual license applications such as Adobe Photoshop, Adobe Illustrator, Adobe InDesign, Adobe Premiere Pro, and Adobe After Effects are no longer available for sale from Adobe.
• UI redesign (all new icons and optional dark UI)
• Auto and background saves
• Content-aware Patch and Move tools (extensions of content-aware fill introduced in previous version)
• Blur Gallery includes Tilt Shift, Iris and Field that can be used to create depth of field effects
• Color Range: skin tone and face detection
• Adobe Camera RAW 7
• Enhanced crop tool with straighten option
• New properties panel that can be used to vary properties of adjustment layers
• Enhanced video support
• Oil Paint filter now ships with the program
• Adaptive Wide Angle filter
• Paragraph and Character Styles
• Built in support for Middle Eastern languages
• Updated Printing UI
• 3DLUT adjustment
• Overhauled vector tools including stroking of vector paths, dotted or dashed
• Snap to Pixel for vector tools and transforms
• 3D UI completely redone, now easier to use
• Last release for Windows XP SP3 and Mac OS X Snow Leopard

CC2014

• Camera Shake Reduction
• Former Extended features now always included
• Intelligent Upsampling
• Camera Raw as a filter
• Editable rounded rectangles
• Improved 3D painting
• Share on Behance
• Conditional Actions
• System antialiasing style for type
• Min and Max filter round kernel
• Sync preferences with Cloud
• Adobe Generator
• Generate image assets from layers
• Edge Reflow integration through Adobe Generator
• Camera shake reduction improvements
• Perspective Warp
• Linked smart objects
• 3D Printing support
• Publish 3D models on Sketchfab
• Adobe Camera Raw 8.3
• Blur Gallery motion effects
• Focus Mask
• Expanded Mercury Graphics Engine support
• Smart Object improvements
• Adobe Camera Raw 8 enhancements

CC2015

• New Creative Cloud Libraries capabilities
• Design Space (Preview) enhancements
• Modern user experience on desktop and touch devices
• More creative options with SVG import
• Enhanced export experience
• Crash Reporter: Crash when creating Character Styles and when saving a document in certain scenarios
• Unable to record the command, Select All Layers
• Tools reset to default set after closing/opening doc or quitting/relaunching Photoshop with Start Screen
• New Swatch > Add to Library check box setting is not sticky when invoked from color picker
• Issue with Cmd/Ctrl key for selecting layers in the Layer panel
• German translation error for Workspaces
• Improved clickable area for dialog buttons
• Export Presets on 2x artboards result in incorrectly scaled assets
• Edit of Library raster graphic in Indesign or Illustrator fails to open the doc in Photoshop unless Photoshop is already running
• Several ScriptUI bugs
• Pasted content centers on artboard when zoomed in to portion of the artboard
• Scripting Support gives an error during launch – Subsequent crashing
• Sampling a color with the gradient tool and panels hidden doesn’t sample the color
• Crash when opening certain .IFF files and hang/crash when opening/closing certain .PNG files
• Unable to drag and drop the artwork from Illustrator to Photoshop (Windows only)
• Welcome screen causes redraw/flicker even if not show if Narration is enabled (Windows only)
• Recent Files stops working after opening 100+ files
• Clicking onto disabled “Start” workspace leads to switching to “Photography” workspace
• Typo in the HangingPunCtuation property used for scripting
• Multiple files are stacked on top of one another, rather than cascaded, when tabbed documents are disabled
• Better collaboration with Libraries
• Match Font
• Updated Libraries panel
• Create patterns with Capture CC
• Improved artboards
• Showcase your work with Adobe Portfolio
• Selection and Masking Space
• Content-Aware Crop
• Export enhancements
• 3D printing to Microsoft 3MF (Windows 10 only)
• Keyboard shortcuts repaired
• Fixed exporting nested layers
• “Rasterize EPS Format” remembers setting
• Embed color profile saved
• Cursor fixed while using transform paragraph text
• Color printing disabled when using App Manage Color (Mac only)
• Fixed file not found error
• Several changes to select and mask

CC2017

• In-app search
• Tighter integration with Adobe XD
• Stock templates, 3D objects, and search
• Support for SVG color fonts
• Introducing Typekit Marketplace
• Better overall performance
• Touch Bar support for Apple MacBook Pro
• Program error when converting to bitmap using pattern dither with a selection
• Performance issues with TrueType and OpenType fonts
• Blank menu entry in the context menu for 3D type
• 3D show or hide polygons issue with Reveal All
• Layer groups with changed blend modes corrupt files
• Touch bar sliders are too big
• Can't write file when you have group ACL for the file on MacOS
• Numerous other issues fixed in the areas of 3D, Actions, Search, Learn Panel, Performance, Touch Bar, and Type
• Scratch Disk size error
• Nik Dfine 2 freezes on macOS Sierra
• Error: Can't save changes to the Adobe Photoshop document before quitting
• The last-used grouped tool is forgotten after using the Move tool (V)
• AppleScript: Open options error while launching Photoshop
• Patches for some vulnerabilities and various other bug fixes

CC2018

• New Stroke smoothing features
• New Curvature Pen tool
• Support for Spherical panoramas editing
• Streamlined brush management
• Access your Lightroom photos in Photoshop
• Supporting variable fonts
• Email or share your creations to several services directly from within Photoshop
• Tooltips have been enriched
• Support for Microsoft Surface Dial
• Upscale photos with AI
• Option for automatically symmetrical paint
• Color Range Mask for Camera Raw
• Healing and spot healing brush lag
• Alt-backspace taking two hits to work
• Character leading broken
• Resize image during place not working
• Selections Improvements
• Advanced Support for Windows High-Density Monitors
• Improved Microsoft Surface Dial support
• Better SVG Compatibility with Adobe XD
• rash while using the Artboard tool after Width or Height is changed to 100%.
• Issues while using the Pen tool with Photoshop CC version 19.1
• (macOS-only) Hidden panel not rendering properly when the user hovers to reveal them
• Crash while running distortion filters against large-sized 16-bit RGB images
• On certain hardware configurations, the canvas draws at the wrong size in floating document frames.
• Crash while changing the Other cursor to Precise when the Magnetic Lasso tool is selected
• TIFF files are written with unaligned tag data.
• Issue while using the Properties panel: The default tracking value is 1 and negative values don't work.
• (Windows-only) Lens Flare preview repeats at 175% and 225%.
• Vanishing Point pixel data distorted while hovering over with brush tools
• Issue while finding the path specified for the CanoScan 9000F Mark II scanner
• (Windows-only) Old font name flashing in the Font Name field of the Character panel when arrowing through the fonts
• The Print dialog box settings revert to default on launch.
• PNG images open with distortion.
• Unlinked layer mask does not resize with image.
• Wrong selection with a hidden layer in clipping mask.
• Smallest swatch size fills large space on screen.
• Mac stylus interaction with panels gets stuck in down state.
• Legacy smoothing re-enables on launch when disabled.
• Images are zoomed in unexpectedly when opened
• Right-Click/contextual menus don't work correctly in Full Screen Mode
• Crash when creating a pin on non-contiguous puppet warp mesh
• Export to SVG gets stuck in processing loop
• Copy SVG from text layer results in error
• Error 'Could not complete your request because the file-format module cannot parse the file' when opening image files
• (Windows-only) Error 'Could not create a new document. There isn't enough room to display this document' when no windows or tabs are open.
• (Windows-only) Focus lost when sampling an image with Color Picker. Pressing the Enter key doesn't apply the sampled color and close the Color Picker dialog
• Relative checkbox state in the Canvas Size dialog no longer saved across sessions
• Eyedropper tool can't sample colors from outside the Photoshop app on Windows computer with NVIDIA drivers
• Artboard Full Screen mode jumps back to center
• Quick Export does not work
• Auto-Complete in File Info does not work
• Print dialog box does not retain settings on next use and the preview appears pixelated
• Video render is stuck at 50%
• WIA support returns error
• Feathered mask displays incorrect value temporarily
• UI doubled in size on Windows 10
• Displacement effects error message: Could Not Complete Request Because of Disc Error
• Images open unexpectedly small with multiple monitor configuration
• Alt+click on adjustment layer does not prompt the New Layer dialog box on Windows
• Steals focus when you run batch processes with the Image Processor on Mac
• Editing and updating smart objects with mask mishandles the Smart Liquify effect
• Vibrance adjustment renders differently
• Select All Layers no longer records in action
• Actions ignore modal control for renaming layer
• Patch Tool functionality issue with recent updates
• Action shortcut overrides keyboard shortcut without an error message
• Crash on splash screen
• Black border don't print
• The dialog box displayed when you save a document doesn't relate to the relevant document
• Rotating a floating image with rulers visible doesn't resize the window correctly
• Color mode when you open a PDF is random
• The limit error message for PSD file size is vague
• Color Range dialog box gets stuck in setting
• View > Fit Artboard to Screen is disabled
• Replace color does not work
• Crash on Nik software in actions
• Retina screen resolution slows path creation
• Accelerator keys broken in Layers Panel context menu
• Color Picker for changing shape colors doesn't work with web colors enabled
• Build up doesn't work when smoothing is on
• Right-click paste function to change layer name to copied text doesn't work on macOS
• Folder.selectDialog prompt text does not set in the dialog box on Windows
• Transform box bounces when you try to transform
• Raw data creates large file sizes
• Paste into Metadata panel is dysfunctional
• Unable to use a shortcuts to Scroll Through The Layers with a European foreign language keyboard
• Levels dialog box auto options 'snap neutral midtones' state resets when you change algorithms
• JavaScript app.batch method ignores specified action set
• Photoshop becomes unresponsive after you add new layers using CC Library
• Artboard Blending options stopped working
• Document status flyout is hard to read
• Layer > New > Artboard won't obey preset background color and stays bright white
• Artboard Tool doesn't scale properly, even when constrained
• Video Render displays the following error: The operation could not be completed.
• macOS picker doesn't load swatch on High Sierra

CC2019

• In the Content-Aware Fill workspace, the sampling area is not fully drawn with some images
• Healing brush and clone stamp tools lagging
• Layer blend modes produce artifacts or incorrect color
• Render video image sequence only renders the first image
• (Windows 10) Color Blend Mode causes a crash
• Duplicated layers get repositioned on the canvas
• Clicking the View Previous State icon in the Adjustments panel or pressing \ key doesn't show the previous state
• (Windows 10) System Info reports incorrect CPU speed
• Photoshop crashes when using the filter Lighting Effects
• Copying layers (and groups) moves them to another Artboard
• (macOS Mojave 10.14) Photoshop crashes during launch
• Intermittent problems using the brush tool painting on a mask
• GIF opens with incorrect number of layers/frames
• Lighting Effects does not work on Smart Objects

Yep.  Barely anything at all.  You might as well go for it.

Bootleg copies can look like they are brand new. Again, I would be very leery of such an offer.

clarification:  I am being offered a new not used copy of CS4 and it is genuine.

Buying a "used copy" of Photoshop sounds fishy.. You may be in for more trouble than you bargained for.

I would recommend that you buy a legitimate copy of modesty priced Photoshop Elements instead where useful tutorials abound. It's a great way to start.

If you can't afford it, you might not want to take the risk of buying a bootleg copy and loosing your money.