The lady vanishes - if you go along and see some agencies, ask who they've worked for, and then you could phone the companies they've quoted and asked which model agencies they use, that's one way of finding out if they legitimately get work.
The warnings about not paying up-front are generally because there are some rip-off merchants who hold "auditions" in hotels, charge you for photos & a model book, then disappear! Prices do vary though among the genuine agencies. You may get charged a nominal fee just to be seen - Norrie Carr charged me between £10 & £20, can't remember how much (after having seen and like the initial snapshot of dd), as they say it discourages timewasters (apparently they've had people not turn up, and people who haven't a clue about what's involved, so if they charge, you are more likely to have done some research and bother to go!!)