Training takes 4,6,8 turns depending on whether it is a school, college, or university level specialty. Does anyone know if you get a bonus for having a high rebel sentiment? I couldn't tell.
I suppose the jist is to try not to build universities unnecessarily because it is cheaper to build three schools and train farmers and fishmen there (and rehab servants). OTOH since statesmen teachers require a Uni and need 8 turns, try to buy several of them from Europe by the time you build it, to get the process underway asap.
Best use for a criminal is scout indian villages can turn them instantly into experts.