Nobody seems to have mentioned the ethics of BTL - the fact is that
it's a low form of capitalistic parasitism - hoping to earn money
merely by owning something that other people need. Providing a service
which nobody wants. Nobody loves a landlord, and BTL is a big factor
in cranking up house prices. Be warned - the bubble may burst at any
time and everybody will have a good laugh at the landlords in
difficulties.

Different if you were building new - that could be a useful thing to
do.

cheers
Jacob