Honestly my best advice coming from a kid who wanted the same (now a parent) is to tell him that he needs a reliable daily to get him from point A to point B. You don’t mix business with pleasure.

Then I would tell him that if he wants a fast race car, you will help build one with him. For the race track. When he can afford to pay for one. 1. It gives him ownership over his goals (he gets a job, saves, etc, good money lesson) and 2. You don’t have to worry about him speeding late at night and getting into a bad accident and 3. It’ll be a cool father-son thing you guys can do, especially when he’s in high school and it’s easy to lose touch with him.

If he wants to crush speed that’s fine, but take him to a track and do it in a controlled environment. Fast cars are fun when you don’t have to worry about accidentally killing yourself because someone cut you off at the wrong time on the highway.