It may sound like a downgrade, but the New Yorker didn't make the switch because he couldn't keep up with payments or because he lost his job. Instead, Lee was nervous about the state of the housing market.

So in March he sold the Manhattan apartment he bought in 2008 for about the same price he paid and moved — along with his wife and child — a few steps away into a luxury, two-bedroom rental unit in a brand new building.