I’m not sure that there’s a good answer to this question. This is very likely to be a money losing proposition in any event. Instead of a productive asset generating dividends, you have an asset with high carrying costs (storage, maintenance, and insurance) generating no income. Any gains have to come from uncertain appreciation.
There isn’t great data on appreciation for collector cars. Hagerty, the classic car insurer, has put together indexes of classic car appreciation. Classic Car, Truck and Motorcycle Values | Hagerty Valuation Tool®
Unfortunately, the data only goes back eleven years and it’s not a great cross section of collector cars. They likely picked cars that they thought would appreciate strongly over some period of time. It turns out, they generally picked pretty well. Since the indexes started, the average car on it has appreciated by about 10.6% per year. That’s pretty good. (Gains are also concentrated in a few winners. If you knock out Hagerty’s two best and the two worst performers of the over 100 they track, your rate of appreciation drops to 9.6%).
Classic cars are surprisingly volatile. For example, the Ferrari 250 GTO is one of the most valuable cars in the world. One sold in 1990 for $13 million and the most recent sales were for $38 million. Ferrari 250 GTO - Wikipedia But, those two points hide the massive plummet in value that took place between 1990 and 1993 when the price dropped from $13 million to about $3 million.
Unfortunately, right now, prices of cars may be falling again. Bloomberg - Are you a robot?
In the long run, I’d expect the value of the average collector car to increase a little faster than the rate of inflation. Once you factor in the carrying costs I would expect appreciation that doesn’t even match inflation. For instance, a collector car insurance policy might cost about 1% of the car’s value to insure each year, though you may be able to get a better deal if you never drive the cars. Classic car insurance may be best policy
So, if I were trying to invest in cars, I’d want to minimize my carrying costs. I’d buy a cheap warehouse in the desert to stick the cars in. I’d drain the gas and put them up on blocks. Throw a cover on them to keep the dust off. A climate controlled storage facility would be nice but the costs of climate control probably exceed any benefit you are going to get from increasing the life of certain rubber or plastic parts. Even things like keeping them all hooked up to battery tenders is probably not worth the cost of the energy over decades especially because the batteries are still going to fail. The same likely goes for schemes to encapsulate the cars in noble gas or nitrogen. At least a nitrogen filled bag wouldn’t be too expensive but the cost to pay someone to keep checking the bags is expensive. Just leave them somewhere and check on them once a year or so. Then hope you’ve picked some winners.
