For weeks, Sixpenny Chimney Sweeps in Woodbridge has run advertisements seeking bricklayers, chimney technicians and air duct cleaners. So far, few people have applied.

"We usually get more responses," said Lisa Mendoza, a secretary at Sixpenny. "But there's a big demand for bricklayers now, and they all want to work just four or five hours a day, have an hour for lunch, and go home early."

Sixpenny isn't the only company in Prince William County and across Northern Virginia bemoaning a scarcity of workers. With the county unemployment in August at 2.5 percent -- and an even lower 2 percent in neighboring Loudoun and Fairfax counties -- employees are in big demand.

Yet, many of the jobs being created are lower-paying ones in retail and services that cater to Prince William's burgeoning population. Even with the unemployment rate so low, applications for food stamps are growing at a faster rate than the population. Social services officials attribute the rise to the huge jumps in housing costs in the county, making even people with jobs struggle to make mortgage or rent payments.

The median price of houses and condos in the county reached $300,000 in August, a big leap from $235,000 only a year ago, according to a real estate trade association.

"There are a lot of people here in low-paying retailing and service jobs," said Lovey Hammel, co-owner of Employment Enterprises, a regional employment agency based in Prince William. "As housing costs have shot up, people have trouble living here."

In Manassas, the number of families receiving food stamps rose by more than 100 to almost 1,400 in August. For all of Prince William, the average number of food stamp cases a month rose by 500 to more than 4,000 for first half of the year.

"We hear the economy is turning around, and I was expecting our claims to go down," said James E. Oliver, director of the Manassas Social Services Department. "But we started seeing an increase in all our caseloads two years ago."

There certainly are jobs, but not necessarily high-paying ones. At Okra's Louisiana Bistro, a Cajun restaurant in Old Town Manassas, there was a sign in the window for two waiters. It had been there three weeks. Okra's pays waiters from a little more than $2 an hour to $6, plus tips.

"Waiters are usually a dime a dozen," owner Charles Gilliam said. "Most people have had a job in a restaurant at some time in their life, and they're generally easy to hire."

Gilliam has had better luck trying to hire a chef. His Internet ad for the job, which pays up to $50,000 annually, drew a dozen applicants recently.

In Loudoun, the number of families on food stamps has almost doubled since the middle of the recession in 2001, from about 700 to 1,350 in July. The county's median housing price leaped to $394,000 from $312,000 last year.

"There are cutbacks in the number of hours people are working in retail and service businesses like landscaping," said Ronald Eamich, assistant director of the county's Social Services Department. "And when you get to a certain point, you start losing your benefits, too, like health insurance, and after a while you come in to see us."

The cuts in hours are probably because of intensified competition, Eamich said. In the past six months in Leesburg alone, Giant Food opened a second supermarket, and some of the checkouts at the first store were then automated; a SuperTarget store opened and a Costco, he said. Giant said that is nothing new and that it's always rejiggering the schedules of its workers, three-quarters of whom are part time. According to the company, the automated checkouts increase efficiency.

The rise in food stamp applications surprised Stephen S. Fuller, director of the Center for Regional Analysis at George Mason University. "Part of this is probably because many of the jobs we're adding aren't helping," Fuller said. The hotel industry is booming, but it tends to hire part time workers, as does retail, he said.

"National retail chains tend to use workers they don't have to pay over 30 hours a week, so they get no benefits," Fuller said. "The average annual wage in retailing has actually gone down."

That is true in Prince William. Paychecks haven't caught up with the cost of housing for many of the county's 173,000 workers. About half of them leave daily for better paying jobs in Fairfax and the District. Those are the people who likely have fewer problems paying their mortgages.

"The high-paying jobs are in those high-rises in Fairfax," said John Hampton, owner of Express Personnel Services Inc. in Manassas. "The reason people are going there is because they can make $50,000 instead of $35,000 here."

That is not likely to change soon. The largest employer in Prince William, Virginia's second-most populous county after Fairfax, is the government. In Fairfax, it's professional and technical services, including tech employers. In Prince William, retailing is almost a fifth of the workforce; in Fairfax, it's less than 6 percent.

Prince William and neighboring counties are adding residents faster than almost anywhere else in the country, which means retail will keep expanding to serve this exploding population. But the jobs don't pay much. At the low end, they pay $7.50 an hour, although some new retailers have started paying as much as $10 an hour, said Ron Stevens, of the state unemployment office in Woodbridge.

"With the unemployment rate low, we still get a lot of people looking for jobs," Stevens said. "But they're people with jobs who are looking for a better job, or one closer to home."

One of the retailing workers receiving food stamps in Manassas is Heather Stevens, a 24-year-old single mother of two. Stevens said she was laid off two days before Christmas from a clerical job paying more than $17 an hour. She now works at a donut shop for $6.50.

Stevens said she is stretched and has been looking for months for something that pays better because she doesn't want to have to leave the county in search of cheaper housing.

"I send out five to 10 resumes a week," she said. "I get responses sometimes. But I haven't got an interview yet."