Set some limits. Each person can own one primary residence and x number of secondary dwellings. Each additional dwelling is taxed at a higher rate than the one before.
People can still buy themselves a house and maybe another couple houses or condos for their family or investment.
But big landlords can’t profitably buy up neighborhoods then crank up the rent. Or perhaps they can own them, but they’re required to be non-profits and expenses and rents are highly controlled relative to income in the area.
It’s a tough problem to solve though… Huge apartment buildings do have economies of scale that permit high density living.
And property owners who don’t sell or develop their land at all because there’s not enough incentive are a big problem in other parts of the world.