Limiting who can create adverts in either marketpress or classifieds via prosites

Hi folks.

I am creating an educational site, where teachers can adevertise for students and students can advertise they are looking for a teacher, I want students to be able to create adverts for free in classifieds and say pro level teachers only could create adverts in classifieds or sell material via marketpress. Would this be possible via pro sites as making the plugin availiable for only the user stypes?