I know a few portolio owners who are buying up property in Manchester and renting to the local authority for asylum seekers.

The council will guarantee rent for 5 years plus voids.

Worth looking into.

Edinburgh is another place, i believe the council give you an incentive to use your property and also guarantee rent plus voids.

Once they are done with your property its written in contract that they will decorate your property back to its original state. (just in case you get some mad folk renting and they trash the place)