One thing I was considering asking is for him to let me buy it, but with the agreement that if I found a major problem, I could return it for a refund within a short period of time (maybe a few days or a week). Then, take it to my cousin's shop that is about an hour away and have his mechanic give it a thorough inspection to make sure I didn't miss anything. Not sure if he'll agree, but I figure it can't hurt to ask.