one can combine the above issue with the force recording of leases to require every unit to pay a "residence" tax that if not recorded as being occupied by someone other than the owner is assumed (even if owner has other place of residence) to be occupied by the owner.
This does a few things. 1) it encourages the owner to rent out empty places, as empty places are no longer simply lost opportunity cost, but actually cost money in what they have to pay in this tax 2) requires people record who is legally living in a place to avoid these issues 3) enables areas to discount this tax for poor / disabled (or other logical reasons that they already have procedures for) for people who live in the area that they want to support.
This does a few things. 1) it encourages the owner to rent out empty places, as empty places are no longer simply lost opportunity cost, but actually cost money in what they have to pay in this tax 2) requires people record who is legally living in a place to avoid these issues 3) enables areas to discount this tax for poor / disabled (or other logical reasons that they already have procedures for) for people who live in the area that they want to support.