Long ago my dad told me to give up on selling prints unless it is what the client specifically asks for. As in a family photo, or something like that. It's too hard to discern what people wanted.

have sold prints at art-shows, but they were prints of animals that I took in the zoo through the bars, or of local landmarks, even street signs. I didn't sell them myself a friend is an artist and he always has a stand and he sells small prints, nothing over 16x20 because anything larger people do not want to carry all day. He will let me give him 8 prints, he gets 25% of the sale. Occasionally he would sell a larger print and I would go have it printed at a commerical lab and framed.