Perhaps, the dynamics of a system like that are impossible to fathom beyond abstractions, especially if you've never observed a similar situation (I haven't). I

Perhaps, the dynamics of a system like that are impossible to fathom beyond abstractions, especially if you've never observed a similar situation (I haven't). If it asymptotically reaches a relatively small subset of all renters, and it never becomes the main place renters go, then I don't think there will be a tipping point.