https://en.wikipedia.org/wiki/Land_value_tax

This is part of an economic philosophy known as Georgism.
The tax is not based on ownership of the land, but a tax from
restricting others from using it.
The situation is framed not as a tax on a property right, but as a tax
on a monopoly right granted with the public.
You’re granted a monopoly in exchange for contributing money to the public.

Also this is interesting:

http://www.dailykos.com/story/2012/02/03/1061611/-STUNNING-When-a-Single-Image-Cuts-to-the-Core-of-an-American-Injustice

24 empty homes for every homeless person as of 2012 in the USA.
These homes are owned by real estate speculators and banks, going unused
because the property holder finds it more profitable to lock them up
than to let anyone live there.

http://online.wsj.com/news/articles/SB10001424127887324412604578515382905495900

http://seekingalpha.com/article/271265-the-phantom-growth-of-chinas-ghost-cities

Also Chinese ghost cities which exist only to hit GDP targets in a
country of 250 million rural poor.

Now there's a lot of discussion about universal income in places like
Switzerland, so money is given to poor to pay landlords rent. So the
government in this case is effectively subsidising landlords.