What can he afford?
Frankly he is more likely to be careful if it is a car HE paid for.
My first car was a 1965 Sunbeam Imp. I paid $550.00 for it (I borrowed $200 from my father) and I paid my insurance) It was a loaner car 875 cc engine that could almost make 65 mph with the light weight 1,200 pounds of car. It had a 11 gallon tank as I recall. I had that car about 10 years and 120,000 miles.
Too light to be safe? I was hit by a Greyhound buss on the freeway one night (the driver was new and fell asleep.) No injuries and after I sold it to a co-worked he fell asleep at the wheel and run into a GM Impala at full speed. It was a rear engine car and he only had a scratch.
I only say this because if the kid knows it was his money he is more likely to take car and not all cheap small cars are unsafe.