I teach Bio, G Chem, & Verbal for PR. It's $20/hr ($50 per class), but you get raises after your first class based on student evals. You generally need an 11 in any section you wish to teach (but if the people in the office like you or think you'll be a good teacher you can get away with a 10). If you don't have 11 or above in any section, you can teach for Kaplan with a 10.
If you want to teach, they'll bring you in for an audition where you teach a subject of your choice for 5 minutes. I personally chose pimping, something I was familiar with. If you pass audition, you go into training for 1 weekend where you get paid minimum wage. At the end of training you have to give a lesson to your trainer & if you do well, you will be certified.
I would definitely suggest teaching for TPR while in medical school. Almost all of the teachers I know are in med school right now. The money's good & it's really only the 1st time you teach a given subject that it requires a significant amount of your time. After that, I've already made myself notes, so I glance at them for 5 minutes before class starts & then I'm ready to go. Hope this helps...