Creative Cloud Pricing

My wife is a retiring Graphic Designer and uses mainly Photoshop. But she occasionally uses InDesign and Illustrator. If we bought the three produts separately they are more expensive than the entire suite (which is too much for us to buy now that she is pulling back on the design jobs and the prices have increased). Is there anyway to just buy Photoshop and still use the InDesign and Illustrator files without having to save 25-30 years of files to PSD files so they can be imported if needed? I looked at importing files into Photoshop and they all say saves the files to PSD files and then you can use them. 

Sorry if this is in the wrong forum

Thanks,

Brian