> And suddenly one landlord owns ten companies trough subsidiaries and trusts. This is yet another nice trick that won't work.
If you own anything that owns property (and etc. down the chain) then you pay same progressive tax on all properties owned directly on indirectly (minus the tax already payed by subsidiaries if the lawmaker feels so generous, he may not be, because why not discourage creative ownership).
> Besides, price and demand curve would still apply where it was one landlord or hundreds.
Sure, but if ownership is not that beneficial for large capital holders then less money is used to buy properties. If there is less money and same amount of properties then prices drop. Then more individuals can afford properties, and demand for renting is lower and rents go down.
> What would help is to encourage housing density to increase supply. That has two main drive: building regulations (mandate building of a certain height) and taxation (tax building by footprint and not by height/units)
If there's more property to buy but plenty of capital to buy then big landlords just buy more and hold, even empty property. Higher supply would probably drive down price a bit, but not as much as you'd expect.
The problem is not only insufficient supply but competition between people who have too much capital and people who have barely enough. First group just drives the prices up for everybody, as high as the other group can barely suffer through.