I'm not sure if that fits the legal definition of prostitution, but I think prostitution should be legalized, so I guess it doesn't matter much. I don't think this is "wrong", as long as both parties enter into this agreement consentually.
If I was a poor college girl, and had any looks at all, I'd be stripping and making retarded amounts of money. Then, no longer being a poor college girl, I'd buy my own place.

I don't think I'd go so far as to rent out my vagina.