Hello ,
Your idea is unfortunately misguided, unless your vintage cars are worth over €100,000 and are expected to increase significantly in value.
In your case, renting is always cheaper, or you have to find an old barn with 20 parking spaces, buy it, and rent/sell the remaining spaces yourself. But even then, caution is advised: if you buy poorly and underestimate the effort or miscalculate, you will lose money.
It also depends on whether your two models will actually appreciate in value or are likely to depreciate, and how much (annually). There are many vintage cars that are value-stable but do not appreciate – then owning your own garage is definitely not worthwhile.
Best regards
Dirk Grafe