do yourself a huge favor and don't buy a car from a friend or family, it only screws up friendships in the long run, and don't buy cars from high school students, as they tend to beat the hell out of cars real bad, i beat my cars in HS and i'm sure a lot of others have done it too.
try to buy used cars from adults who look as they have the means to take care of the car, so you don't get stuck with a money pit, and have a real mechanic check it over, who ever you buy from, its $100 bucks worth of insurance in the long run.
just my 2 cents.......