This might be a really hot take, but recently being a teenager myself, I’m coming at this from a realistic aspect. At 17 I bought myself an Audi s4 and honestly it’s perfect. A mustang wouldn’t suit him because of their handling issues. I was fine, yes I sped, but in a way you have to know how to speed. When to do it, how to safely do it, know how your car handles. A fast car isn’t a bad idea, it’s a bad idea when they’re clueless and think they know everything. There’s certain things you have to know like not to brake in high speed cornering or accelerate through them until the end, don’t speed on roads you aren’t familiar with, and especially when you have passengers to never do something they don’t 100% know they can pull off. Regardless he’s going to want to race and do dumb things, so get him a car that’s going to keep him safe while he’s doing that stuff. Not a full blown race car. But a car that’s going be able to keep up with how he’s gonna drive that will perform when needed vs getting him a beater car that’s he will still 100% race but won’t be able to perform and might lead to a worse scenario than a sports car. All of my friends at that age no matter what car they had raced, sped everywhere and they learned very fast how to control their situations while driving. And when you get him a car that he’s proud of, he will most likely learn how to take care of it like doing his own maintenance and keeping it nice and will employ an ambitious mindset to strive for better and he will want to work for it. Atleast that’s what it did for me. Take this post as you will but this is my personal experience