What is the point of a 'free market' if houses are left empty?

The whole idea of a free market is a complete lie:
surely the laws of supply and demand apply to housing,
so that if a house is empty its (rental) price should go
down until it is occupied.

This won't happen partly due to greed but also
because it would make enfranchise the very
people at the bottom of society-a homeless
person could pay a months rent for two quid.
If there are fewer homeless this way it may
be more difficult to evict people/they would
be paying much less than anyone else does
for a mortgage so the people least likely
to own a home can have virtual ownership
of one!

The reason this doesn't happen is the need
by capital for continual exploitation: workers
have to earn more money and work full-time even if
they live in poor housing.