I waited till I was 23 and done with college to buy my M35A2. I've had my 1963 jeep and numerous other Jeep toys since I was 15 though. I would recommend starting there. They're small, simple, easy to drive, and very fun to own. Looking back, no way on earth did I have the maturity or capability to own a deuce. Between drinking, peer pressure, and stupidity I would have been in jail or dead. I also had a lot of experience by your age driving tractors, dozers, dump trucks, and so on but that is very different. Getting out on the road, moving at high speed, and risking not just your future but everyone else's requires a lot of thought.
Also, no way could I of afforded it. A tank of diesel is $200. Holy crap when I was 16 I used to work on a farm like a crazy person for most of a week to get $200. I was smart about things, or just plain lucky, and I went to college for engineering, and now I have a job where I push around a computer mouse and make that much money in a few hours (you ARE going to college for engineering, right? - if you want some guidance on college and engineering - send me a PM).
Having a deuce as your only vehicle is just plain stupid. They require a ton of maintenance, that you can only avoid so long before it bites you in the rear. I'm 25 now and I love my truck, but when it breaks down, I have numerous other vehicles to fall back on that I'm not borrowing from my parents or a friend.
In conclusion, buy something else that you can still enjoy, quickly repair, and afford, like an older jeep, or full size pick up. Also, I was not the kid with the biggest lifted truck in the parking lot in high school and I was ok with that. I had jeeps that would make those trucks look like completely useless mall crawlers in the woods.
PS: One more thing. It might sound like some people here HATE people from the age of 15-18 that want to buy a deuce but they are just not sugar coating the truth because that's what grumpy old people do. They're on the other side of the mistakes you may potentially have ahead of you, they suffered the consequences, and they're trying to recycle their experiences for your benefit. Part of me is thankful for the mistakes I made and WANTS other people to make those mistakes and learn life lessons, but any more, with civil litigation so prevalent and DUIs that haunt you forever handed out like free candy on Halloween, you can't afford to make those mistakes that previous generations took for granted. Welcome to the brave new world I guess.