I have a friend who is now shacked up with her ex customer and they appeared very happy, at first, although I do feel that the cash he gives her on a weekly basis, housekeeping money, helps as she couldn't handle this job at all and was drinking all the time to help her cope with it. Although he is pretty controlling with her and now doesn't like her being friends with girls that work, which, if you ask me is damn cheeky of him, he's also very needy and goes in huffs all the time and I genuinely believe that she stays with him because of his money and the fact that she'd have to go back to work if he wasn't there, she has 3 kids and can't live off of a normal job now.
Personally I couldn't date a client, I just wouldn't be able to take him seriously, and I'd expect that he'd see me in the same light, and I'd always wonder what his true intentions towards me were.