DarkJak

I got my pre-owned 370Z from my parentsfor getting a full ride to my school, instead of something more parent-friendly, like a Honda Accord, and the gas and maintenance is manageable with my summer job working 40 hours/week. I can assure you though, unless you can find a job that gives you at least $10 an hour and full time, having to pay for insurance and car payments on top of that would be stressful. I can honestly say that if I were in that position, I'd have went for something much cheaper, like a very used 350 or S2000, which are both as fun to drive.
Tires are going to be a big hit too. They put a big dent in my modding plans when I had to get new ones.

That said, it's definitely doable, but you'll be working full time just to support your car, which is a huge load to have in high school. Doesn't really leave you much time to drive it either.

FWIW, my first car was a 2006 V6 Camry, which really helped me respect the 370Z when I got it. Haven't f'd up yet!
My insurance at first was over $100/month with perfect record and several other incentives. Also, adding nav in later would be hard as hell if you are going for the factory nav system. I haven't seen it done yet, as most people get aftermarket systems.