Affordable housing is an issue at the county, city and neighborhood levels. It keeps the economic integration and diversity that enables a neighborhood to maintain a middle class — another key element in a solid economy.

"Something about that middle income establishes stability," said Eddie Latimer, executive director of Affordable Housing Resources Inc.

To an extent, the 1990s economic boom hid the downside to rampant economic growth — escalating real estate prices and rental rates. The economy slackened, and the issue has come racing to the foreground.

"I'm seeing that there's becoming now a more distinct difference in the haves and the have-nots," said Chris McCarthy, executive director for the Nashville Area Habitat for Humanity, which builds and sells homes for low-income people. "Fewer people have been able to achieve homeownership."

"Affordable" is a relative term. The quest for affordable housing has led people to move from California to Nashville; from Nashville to exurban Smyrna, Tenn.; from the urban and trendy Nashville neighborhood of Hillsboro Village to more rural Antioch, Tenn.

Bret Comolli, chief executive officer of wireless services company Asurion, pointed to Nashville's lower cost of living as one reason for his company's decision to move its headquarters from northern California. When asked how the cost of living compared, Comolli said, "The scale's not big enough."

The U.S. Department of Housing and Urban Development has a standard definition for who qualifies for affordable housing: when the rent or mortgage costs no more than 30 percent of a person's take-home pay. Families earning 80 percent of an area's median income or lower qualify for assistance in some fashion.

The word "affordable" often carries with it a negative connotation that to many means public housing or Section 8, a HUD program that allows "very-low income" people to live in apartments or single-family homes.

The face of affordable housing, however, might surprise many people. Those eligible include police officers, firefighters, healthcare and daycare workers, teachers, administrative assistants or maybe a chief executive officer's secretary.

Potential homebuyers or renters may not know they qualify for a special deal, whether it's down-payment assistance or income-based rent adjustment. And real estate agents aren't fully aware of the myriad programs available.