This is a very good point - many normal purchasers will be selling a house at the same time that they're buying one, so there's a net zeroing in additional hous

This is a very good point - many normal purchasers will be selling a house at the same time that they're buying one, so there's a net zeroing in additional housing demand. Renters who are buying a house will leave a rental unit open, and cause a tiny decrease in rent prices. But investors frequently just take housing off the market, and contribute to a shortage. And as with most life necessities, housing is somewhat inelastic in terms of demand, so shortages cause skyrocketing prices.