However, in the mainstream world, an agent usually has a signed contract. Not sure about it in porn, especially since you see some of the same girls on different agent's sights.

BTW, wasn't Roy Garcia a while back stating that he was going to expect a fee no matter what as long as he discovered the girl. Like even if she hadn't gotten a booking from him in three years, he'd expect payment from the company. Of course, I figure most people would tell him to shove it. But I don't remember the exact stuff, maybe Gene Ross or lukeford.com has it archived.