The problem with this approach is the impact it has on areas that have availability problems, and where there is more demand than supply for housing (think big cities that are experiencing condo booms).

In those high-demand areas, owners will simply pass those tax costs down to their tenants, and the rents prices will go up, leading to even less affordability.

If you combine that with looser zoning regs, the higher rents will make building more housing more lucrative.

In my mind, I was separating out homes for rent from investment and second/third/so-on homes. Although, it seems tough to separate those out since investment homes and non-primary homes are often rented out, although sometimes not permanently or continuously as homes specifically treated as rental properties. It needs some more thought, but I don't like the no holds barred approach that takes place right now. I in general don't like homes being treated as a business and investments, and I think it should be discouraged. Apartment complexes are a little different. Even there though, renters need better protection. One of my friend's rent just increased by 25%. It's ridiculous.

Make the tax scale with number of homes the entity owns.

They might not be able to find someone to pay that rent. In which case they might be forced to sell. Ideally someone who doesn't own a home will purchase it and won't have to pay the tax that caused the original owner to sell.

So you punish renters for the benefit of prospective homeowners?

Not everyone wants to buy.

Every time a housing discussion comes up someone comes in with this argument. If you stopped to think about it you'd realize how silly it is.

Renting doesn't need to be handled solely or even at all by the private market.

Sadly I don’t see any better way to help renters.

If you make the costs of real estate investment so onerous that it’s only attractive to owner-occupants then it becomes far harder for your landlord to exploit you as a tenant, as the option for you to buy much more cheaply will be there even if you choose never to do so.