I agree with Prague, and Mark. I've never done it either. I think that it is unethical, and unprofessional for starters.
But the biggest reason is your reputation. If you fuck over some girl, she will run her mouth, and ruin your reputation making it hard to get more girls later. So it's not worth it when you do this full time. Especially if you are in a smaller town.
it's VERY tempting at times, make no mistake, and the girls do come on to you. But you have to refrain thinking about your rep, business, and do what's right.
