The more the people who walk out their homes, the more renters are there in the market. Thus the pool of renter will get bigger. At the same time, houses that were originally put to rental market by desperate owners will become hooked on the foreclosure procedure that will take a long time before they can be used as rental units. Thus the size of the rental market will be sort of steady. In the short term, rent will increase in SD if more homeowners that are under. That is my guess.

Surveyour: Indeed banks do recycle their non-functioning assets to rental units when they are desperate.