If that's actually the case, and many of those mortgages are adjustable-rate, then we've learned nothing and another 2007 may be inevitable.

Fortunately, I still believe that the overwhelming majority of new rental units are being scooped up and placed on market by commercial entities, not individuals. You may have many individuals putting their second house up for rent, but I'm skeptical that banks are giving individuals a half-dozen loans in series. With the housing shortage as bad as it is (we're just not building enough to offset our population growth), I suspect that commercial entities would swoop in and buy up most second houses that individuals couldn't maintain anymore.

It is the case, and generally people that are savvy enough to purchase these are savvy enough to lock in a 3% rate when offered.