> Constrain supply and new construction enough, and all that stuff is intensely maintained because building new is not an option.

Anecdotally, from San Francisco, my experience is the opposite. Most units are in terrible conditions, barely painted over. There is no incentive for landlords to put extra money on the place, it will not increase the price at which it will rent.

You end up with high income people moving into shitty housing, middle income moving to the outskirts and low income people moving to the streets. Only the landlords win.