Good for him.
I do say that I am jealous, heh My dream since I was 7 years old and sat in our friend Todd's mid 90's cobra, Ive wanted a stang. I pleaded since I was 13 till 16 for a v6, and it was no go.
In retrospect, now 17, closing in on 18, Im glad for my parents making me pay for my 1995 Camry. Good car, good gas mileage. And low insurance. It really made me appretiate it and be careful as the car is in my name, insurance is in my name, and any other misc expenses are my responsibility.
The lesson they taught me is simple, you want something, you earn every bit of it.
The day I got my car, my dad tought me how to wax, buff and polish. During the week he showed me how to do my oil, and when I needed my filters replaced, he got me a Haynes manual.
I know Im a youngster myself, but make sure to teach him how to take care of his mustang. If I started to let mine go, he took my keys. This made sure I always kept it clean and maintained.
Hah, I dont know what he would have done to me if I would have wrecked it. :P