I would let him have it. If he seems to be mature about driving I wouldnt worry too much. You got too consider tho that the car is over 30 years old and may leave him stranded somewhere if its his daily driver. My brother is 17 and i let him take out my 302 mav all the time and nothings ever happend. On another note back when i was a teenager in school I got in a lot of trouble and messed with a lot stuff i shouldnt've, but if i had a cool lod car like a mav or something to work on or hop up that woulda been my priority and wouldve gotten in a lot less trouble.
you need to check for rust on the floors and in the front cowl what you need to do is take a gallon of water with you and poor it into the vent and look for any water leaks in the car if it leaks i would not buy the car this is what rust's out not a easy job at all http://mmb.maverick.to/showthread.php?t=35489
The Maverick I have was my daughters 16th birthday present back in 1992, she drove it all through highschool till she got a new Ranger to go to college in 95 when I inherited it back, no problems with the v8 allthough the boys were always trying to race her,1 time she did a 180 spin in it but it was because she almost ran a red light and locked the brakes up, just be sure the car is safe and the rest is up to him, 1 ticket for contest of speed or speeding will bring him back to earth if he has to pay for it,lol