Well-established effect and it applies to everything. A huge portion of all technological improvement/productivity gains and nearly all public investment money ultimately accrues to land rents which we then later just call "the cost of living."
In order for the economy to function there has to be ~ SOME ~ landlords. In my experience the random people that rent out their second property are usually good landlords, whereas the massive players treat people poorly. If this tax were implemented well, the latter group would be taxed more forcing them to stay honest. The small landlords would have a competitive pricing advantage over the big players, which should go a long ways to keep rents fair.
> In my experience the random people that rent out their second property are usually good landlords, whereas the massive players treat people poorly.
I don't think there's really all that much of a difference. Small landlords have low cash problems (slow repairs, stupid disputes on damage deposits, etc...). Big landlords have policy and bureaucracy problems (we forgot you were disabled and removed the ramp from the deck, we evicted the wrong property).