I wouldn't consider these investment properties occupied. And in fact, that's the point of my suggestion. Excess liquidity accumulated by the upper echelons o

I wouldn't consider these investment properties occupied. And in fact, that's the point of my suggestion. Excess liquidity accumulated by the upper echelons of society is spurring this "housing crisis". Society has an interest in dis-incentivizing the kind of property-hoarding that you describe. In addition to wanting to keep housing affordable for workers in cities and elsewhere, cities should be scared witless by the thought of "ghost towns" and neighborhoods with 30% residency. Cities are not collections of streets and buildings, they are made up of the people that reside in them, and without people, the economy of a city will collapse.