would girls actually pay you to give you head? I don't think so. I'd imagine getting slime blown into your throat would not be pleasurable.
Anyways, I wouldn't sell oral to strangers cuz of std's and what not. Sex I'd charge... wait a sec, why would I sell myself? Most likely it would be to some fat chick with a mustache. When I can just get some from a good looking girl by spending a given amount of time courting her?