In many first world capitals, it's actually a common investment to buy real estate and not rent it out at all. The running costs are lower, there's no maintenance costs and no one pesters you about miscellaneous issues. All these people do is sit on the homes and wait for them to go up in price while everyone else struggles to find a place to live. Them not renting out reduces supply which further drives up prices. You don't see them up for rent because that's not the business they're in, they're in the buy-hold-sell business instead. It's a good example of ridiculously perverse incentives, and why the regulation needs to be changed to make this a thing of the past.