There just should not be landlords

Fuck cars

Fuck landlords

How are you supposed to keep them from passing on the cost of taxes to their tenants?

You have to realize that they still "own" a limited resource that lends them power to leverage over others. The only way you make this abuse go away is to have the people collectively own the land. Any accommodating regulations you place on landlords will only be temporary until they are worn down and removed.

The amount of vacant units in cities where people actually want to live tends to be highly exaggerated (Manhattan is generally sitting somewhere around a 5% vacancy rate), but twisting income tax into some weird kind of tax on unrealized value is administratively messy and completely unnecessary when we already have much simpler solutions in the forms of land value taxes or even basic property taxes. Not to mention, increasing taxes on rental units just increases everyone's rent, which is a rather odd strategy if the aim is to make housing more affordable.

People really will propose literally anything except the wild concept of building more housing.

I don't know about this, but the non occupant owners should have to pay obscene property taxes and then reduce the rates for owner-occupants to a reasonable level.

The state should stop enforcing the legal rights of landlords to own property and exclude people from its use through physical force, and should organize the people enough that they can defend themselves from retaliation to this change.