This is where you're wrong. It's the other way around.

Asset pricing is what's correlated to rental affordability. If the tenant class, in general, can't afford rent increases, rent won't increase, and real estate asset prices will stop growing, all other things being equal. Obviously, if money becomes cheaper for landlords, then they will borrow more of it to buy the same properties. But this does not give them any more power to unilaterally set rents.

But all in all, the tail does not wag this dog.