This changes quite quickly if the homeowner is living in a home worth less than their mortgage (underwater - can't move) or if they can no longer afford to pay

This changes quite quickly if the homeowner is living in a home worth less than their mortgage (underwater - can't move) or if they can no longer afford to pay their mortgage (have to move / declare bankruptcy). Having to shift to another rental property is a relatively small jump by comparison unless you have to shift school districts due to lack of inventory. How much risk would you take on to ensure your landlord can't kick you out?