Not sure about how common prostitution is in students, but a couple of years ago, I and a friend were approached by a guy on campus trying to hire us as escorts!! We told him where to go, but sadly I think it may be an option for some. I've run into financial difficulties whilst being at uni, and it's never been so bad I would resort to that, but I imagine if you're really desperate it could be something you can fall into...
Also, why would the fee hike cause this? You don't pay them upfront or anything.