If local zoning already governs what may be built or operated on a property, what principle allows a government to levy fines for lack of use of a property that has been built and maintained to the required zoning? (if to all other requirements, the property is not derelict, in poor condition, a blight or public nuisance?)
I didn't think that you could be compelled to be a landlord.
(By the way, Oakland also is attempting to put in place such a regulation, but to my knowledge, they have dumbed it down with so many exceptions -- elderly, destitute, social justice, etc. etc. that it's meaningless)