The owner of an apartment is always receiving income from it, either in the form of the rent check or whatever utility it provides for him to keep it to himself.
I don't like land taxes and other property taxes because I don't think there's a good way to apply those taxes progressively. Rather, if we just take the imputed rent of a given asset (land, building, car, etc.) and add that to the taxpayer's income, the the progressive income tax can just do its thing.