Porn for paysites was profitable enough to help pay off a mortgage, according to one of the artists at superheroinecentral.com (who no doubt has a day job). Anton Kisiel makes a respectable side income selling his outfits/hair but doesn't live off it. Selling prints at art fairs/renFaires/SF cons looks like the best bet but you're looking at the investment in a decent glossy color printer (I'm fond of my $150 Epson 785EPX) and a shrewd feel for your market's tastes (not your own). Nekkid Vicky with a blaster on a dragon in a temple fronting a Bryce landscape may not be your cup of tea, but this is a business.