I hear this argument a lot and it's a trick to get the libs to not support taxes against landlords. In this situation, rental rates are dictated by how much the market can bare because there just aren't enough houses. Prices are set to the maximum so landlords would bare the cost of the tax rather than renters. If the taxation threat was real and long term enough, it would incentivize landlords to do something with empty units, rather than it not costing them anything to sit on it.