I say start small and realistic and see where it goes. I recently started promoting my part-time photography business a bit more and lo and behold.. I've been quite successful the past few months making more $$ than I really expected to... and the best part is.. I'm having a great time with it, learning a lot in the process and meeting some terrific folks. I didn't have very high expectations but just kept at it and it worked out. If you have a good product that is in demand, then you should be sucessful.

In your case, the start-up costs to do this is very low (assuming you already own photoshop).. Just purchase a domain name, some web space and create yourself a nice website. Use paypal as a back end for credit card sales and also except orders via email. For as little as $10 a month, you can have yourself a working shopping cart website and all it takes from you is the content and a blog.

Good Luck to you!