I was 18 (i still am) when i bought my 12 WRX. I have been working since i was 14, and I always worked at carpentry (first summer of work) and landscaping for each summer since, so i always had a good income (for a teenager). I always had a dirt bike and a quad, but last spring i sold them both, and put that money, along with some money i had saved on a down payment for the car. I am in college doing plumbing now and still work part time at landscaping and i am going to be snow clearing this winter.
If you really want something, you can make it happen.