home made cactus.

Also if you use a search engine and look up 'howto draw a catus with Illustrator' you will find many video tutorials. Here are a few...

https://www.youtube.com/watch?v=f_xN2wuiFoM

https://www.youtube.com/watch?v=KFAoPW2UZUQ

https://www.youtube.com/watch?v=XQuIgiqQBRI

Now it's not ready for sale.

That's what you could do:

1. go to the nearest real cactus and draw it from some different directions to find the best and most impressive look.

2. Scan the draw to have it as a template.

3. Do some research to find the stylization. Creating the photo-realistic images in Illustrator is possible but takes much time and skills, it's not for beginners. And anyhow the vector images generally look better when they are stylized. But "stylized" does not mean "look like a 5-year-old child's drawing". So try to find a nice style for your art.

4. Practice using the Pen tool and understanding colors, fills, and strokes.

Good luck!

[Moderator moved from Stock Contributors to Illustrator.]

Can you draw?

Can you paint?

How much art schooling have you had?

If you're just starting out, I recommend tracing some real-life images to get a feel for the tactile textures, lights/shadows and colors you see in natural cactus plants.  Use colored pencils/pens or water colors to add some depth to your drawings. 

Hope that helps.