Oh, don't worry, they also buy land to build luxury condos for the upper-upper class - that can't buy but can still pay rent.

>But if there are 100 homes and 10 people, it doesn't matter how rich they are, the prices will drop because there is less demand

No, the price won't drop. The market is extremely inelastic. These homes are collateral for other investments of the super-super-super rich (people or organisations). It is better to keep them vacant rather than drop their value by lowering the rent, which would cascade to their leveraged investment.

This is why: - rents only go down when there is a big generalized financial crisis, otherwise they never go down. The best that used to happen was that rent stayed stagnant while wages rise, but that isn't happening... - you see so many empty appartements and retail spaces everywhere.

I mean, there a a HN front-page story about vacant spaces a day ago. You should read it.