A tan 1956 Oldsmobile 88 coupe. Paid $60 for it in 1966. Sold it a few months later for $100.
At that point, I thought making money with cars was easy and fun. I didn't even have a license when I bought it or sold it.

When I did get my license a year later, my first car was a black 1959 Cadillac convertible. Paid only $260 for that one. If I had it today, it would be worth over $50k in nice shape...

Neither one of these were mine, just photo examples.