Most Princeton Review offices do not have a minimum MCAT score. Instead, they require all applicants to take and pass a content exam in the area they intend to teach. Applicants must also teach a 10-15 minute mini-lesson, which usually has to do with their subject area.
After that, there are two additional days of training / auditions where each applicant must teach multiple lessons and passages. At the end of all that, you find out whether or not you meet their expectations.
I found mine via craigslist post, and submitted a resume to them online.
TPR does pay for training - something like $8-$10/hour. They also cover all expenses associated with training (airfare, cab fare, hotel, meals). Once hired, pay is generally around $20/hour for large group classroom education, $25/hour for small group or individual tutoring, and $8-$10/hour for promotional events like tabling.
Granted, those are the starting rates, and there is the potential to make more once you become more experienced.