You would have to showcase your quality too. Quality is very important. IMO I think it would be a money pit. What if the quality of the prints aren't as good as I can get at an online lab? You'd have to refund everyone who ordered and would have to eat the ink, paper, and time costs. Really need to weigh the feasibility.
That site Steph posted is good. I don't go there (don't have the link here) but the prices are the same. $4 for single sided 12x12 + shipping.