The limiting factor is, roughly speaking, wages. Assuming landlords actually want to rent their properties out, the rents will go up to the maximum people can a

The limiting factor is, roughly speaking, wages. Assuming landlords actually want to rent their properties out, the rents will go up to the maximum people can afford/are willing to pay - I'm not sure the distinction matters - and then go no further. (And it's possible they are already at that level, or near enough. It is after all the price point that a seller always tries to hit...)