I have sold quite a few photos a local art exhibitions and local cafés both framed and unframed, Clip frames are the simplest way of framing them, if you go for proper frames you would do well to use a card mount and all the other paraphenalia of framing. I used to print mine on an A3 size printer using non fugitive printing inks. People won't pay more than £50 for A3 or £30 for A4 sizes. If you are careful with your printing and don't make too many mistakes you can expect to make about 100% profit, not counting your time.