For both deal-makers and the construction industry, the recession and the housing mess that powered it have turned the focus on rentals. That often is a a synonym for "multifamily," but more than a quarter of the U.S. rental market is single-family homes.

The overall breakdown is shown in the National Association of Home Builders' accompanying chart.

As the year is winding down, NAHB looked back at what it found from the Census Bureau's 2009 American Housing Survey. It showed that 27 percent of rental units were single-family homes, and another 6 percent of the stock was attached townhome-type one-family housing.

It's very unlikely that those numbers have gone down any as foreclosures have continued to turn homes from owner-occupied to vacancies.

"A large share is also due to homes that have been divided into two to four apartments with some common space, representing 20 percent of the rental housing stock," NAHB added.