Investing into a future classic car seems like a good idea. Let's take the BMW M3 E30, one of the best homologation specials on the market. It's an icon of the 80ies touring car scene. Awesome to drive, good to look at, even 20 years after its birthday.
And the value is increasing continuously. The cart shows (in green) how the money you have to put down for an M3 in good shape went up since 2000. And it can be expected that the value continues to increase.
So, this would be an ideal candidate to invest in, right?
Well, no. If you only assume reasonable cost to keeping the car in good shape (garage, basic maintenance, insurance, etc.) you will spend much more money on the car than what you can ever get back for selling it. That's the nature of car ownership. Doing nothing is not an option, storing it outside is a good idea neither.
So if you are looking for a good investment and you don't like stock certificates then maybe consider watches or stamps.
However, if you are also looking forward to having fun then owning a car like the BMW M3 might be one of the financially quite attractive hobbies and that's what it is meant to be. "Freude am Fahren" (driving with passion).