by Ingrid Cummings

Cheryl and James DeBoard of Columbus, Ohio, created the best of both worlds: the peace of mind that came with having Cheryl's aging parents living in an adjacent in-law suite, and the autonomy both parties wanted to retain.

"It was wonderful to have them nearby in their last years," Cheryl says. "When my parents were there, they were totally independent. We made a deal to call each other before we'd visit. No popping over. Neither of us wanted the popping."

The DeBoards' 1,100-square-foot suite also functions as a pool house. They added a pull-off area on the driveway so nobody's car was ever at risk of blocking another — the kind of factors savvy remodelers take into account when building a second living quarters on the property.

With both parents now deceased, the family is looking to sell their home and bonus suite. "All our neighbors have been impressed, and said 'when you move, let us know!'" Cheryl says.

In-law suites — also known as mother-in-law quarters, accessory dwelling units, carriage houses, or granny flats — are gaining in popularity. Credit the recession, as well as growing numbers of aging seniors who are living longer.

According to U.S. Census Bureau data, more than 3.6 million parents lived with their adult children in 2007, a 67 percent increase since 2000.

A November 2009 AARP survey indicates there are 6.6 million multi-generational households in America — a number that's been on the rise for nearly a decade. In 2000, the number of households with more than two generations was just 5 million.

In-law quarters are usually a separate, preferably self-sufficient unit within a main house. They can involve remodeling an existing bedroom and bath to accommodate a senior citizen's needs, or the construction of a second master suite.

Ideally, in-law suites include a kitchen and laundry facilities, along with living and dining areas, a bedroom, bathroom and closets. Think creatively: you can renovate a garage, bedroom, attic, office, basement, back porch, even a barn or freestanding cottage on your property.

When executed well, in-law suites are a practical solution to multi-generational living, affording enhanced resale value, privacy, security and autonomy.

"An in-law suite needs to be about features and amenities, not necessarily size," says Stephen Melman, director of economic services at the National Association of Home Builders. "Don't get hung up on square footage."

The best grandparent suites, as Melman also calls them, incorporate universal design, useful features such as wider doors to accommodate a wheelchair, grab bars and curbless showers.

Many new housing developments are including in-law quarters with separate suites for privacy.

But scores of Angie's List members who took a recent online poll have opted for renovation of existing homes to create comfortable and creative accommodations for their parents.

Actually, it's not just parents. The apartments work well for divorced offspring, disabled adult children, "boomerang-ing" college grads, newly married kids and their spouses, divorced brothers-in-law, or friends in the middle of one transition or another.

Member Cynthia Baer of Atlanta likes the options her suite provides the family. "Ours has a separate entrance and we rent it out," Baer says. "It helps with the mortgage. It's a great asset."

Baer knows one day the function of her flat may change. "If my mother might need to come live with us, or we need extra space, or an office, we could do it."

The cost to renovate an existing space into in-law quarters can range from $5,000 to $100,000 or more, according to industry statistics.

Andy Scott, owner of highly rated Scott's Home Renewal in Des Moines, Iowa, recently renovated an attic for use as an in-law suite and speculates the $25,000 remodel was a good investment.

"Whenever you're adding finished living space, it should help on the value of your home," he says.

On the downside, Scott observes that some in-law suites are seldom used. "This attic we're doing now, the in-laws are there just two weeks a year."

Recouping the cost invested in a suite — as with any remodeling project — isn't a sure thing, say real estate experts.

Some say it's akin to a swimming pool or other extravagant extras that only some buyers desire. But with so many families now faced with caring for elderly parents or housing adult children, the market is growing.

"I can really make an in-law suite into a selling point, but it's a specialized selling feature," says Bif Ward, a real estate agent with F.C. Tucker in Indianapolis. "For the right person, an in-law suite adds significant value."

Member Teri Worley of Portland, Ore., had an in-law suite added for her mother, who has since died. Now, the suite — built within an unusual 9-foot-deep crawl space — is being used as a guest suite of sorts.

At 1,600 square feet, it has granite countertops, tile floors, as well as the usual bedroom, bathroom, kitchen, living room, and laundry area.

"The kids use it for a theater and billiard room," Worley says. "I think my daughter's going to be moving back in."

Another option for those needing an in-law suite is to purchase a modular unit that fits within a two-car garage. Once the need changes, the unit can be dismantled or repurposed into another type of accommodation, such as an office.

That kind of multi-functionality can be a big asset. As one member in Alabama quipped in response to our poll, "We built it, but she didn't come!