Well, based on the rules of the thread, I'm at 9 years, but I bought my first car, 1991 Chevrolet Beretta GTZ when I was 14. I had a stereo in it shortly after and sold it before I even could drive it legally...
I have been into cars as long as I remember, mainly thanks to my dad, who is a huge car buff himself. He has always kept his cars in excellent shape, and now has a mint, all original 1968 Mustang coupe..