I agree with all these answers. I have a 1966 convertible, candyapple red, red interior, 289 automatic, power top. It's in great shape and was recently appraised at $28,500, which I actually believe is a bit low. But that's 10 times what it cost in 1966. What does a new Mustang convertible cost today? More than $28,500, right.
So even if the cars go up in value, you've got to consider today's money verses the worth of the dollar 10, 15, 20 years from now.
Don't buy a car thinking you will make money. Enjoy it. And, for my added two cents, don't pay over sticker or grossly inflated dealer prices. That makes it just that much harder to ever come out ahead.
(By the way, I gave $4,800 for the convertible 22 years ago and probably have invested another $5,000 over the years. I'm dollars ahead but I could not retire on that. I do wish I had bought a 1966 Shelby with 60,000 miles on it that I passed on 20 years ago for $13,000. My wife would not have understood but that car would be worth some serious cash now. I would never sell it, though, unless my health or other needs mandated it.)
BUY YOUR CARS TO ENJOY THEM AND BUY THEM AS CHEAP AS POSSIBLE.