Is a modeling agency legitimate if it requires you to take cles?

I'm interested in modeling, and I've found an agency that would represent me (I've already met with the agent). However, I've always heard that an agency should never require its models to take cles, and that's exactly what this agency is doing. I do know a couple of girls in this agency who have gotten work through the agent (bridal runway shows and photoshoots), and it would seem that several other models in the agency are successful (magazine covers, occasional appearances in popular magazines, and parts on the sets of major movies) and make a decent amount of money. However, the idea that I have to pay slightly upwards of $600 makes me a little weary. Opinions please?