Sherry Mattson, deputy director for programs at the nonprofit Fairfax Area Christian Emergency and Transitional Services has seen families hurt by rising rents. Her agency offers assistance to the homeless or to people who are at risk of becoming homeless. "Most of our clients are single mothers," she said. "We encourage people to look outside of the county, but if they grew up here it doesn't seem fair." Mattson added that it was "unreasonable" to expect a single mother working in the service industry to afford rents in Fairfax County."What we find is that people of these lower income categories cannot find housing that's affordable," said Tim McMahon of the group Reston Interfaith. "So what they do oftentimes is double up with family or a friend. Some of them unfortunately end up in the shelters." Finding affordable housing in Fairfax County is getting increasingly more difficult as rents increase, tenants and aid agencies say. The Rental Housing Complex Analysis report for 2001 compiled by the Fairfax County Department of Systems Management found that the average cost of a rental housing unit increased 16.5 percent between 1998 and 2000 and another 14.2 percent between 2000 and 2001. Average rents for all structure types of rental housing – low-rise, mid-rise, high-rise and townhomes – exceeded $1,000 per month for the first time in 2001. Townhomes were the most expensive, averaging $1,383 a month in rent. Much of that increase is due to market fluctuations, said Mary Stevens, deputy director of the Department of Housing and Community Development. "[Rents] go up because there's a demand for that type of housing," she said. "Even when the market in general is going down, rents in affordable housing complexes tend to stay stable or rise because there's such demand." With the current economic slump, the market for affordable housing has been very healthy, she added, driving up rents. "It was the toughest it's ever been over the past year" to find an affordable home, she said. Rising assessments and the corresponding increase in the property tax rate also has a role in raising rents, said Stevens, although it has not been "the driver for most increases." But Jim Foley of Summit Properties which operates several apartment buildgins in Fairfax County said that property taxes have no effect in rising rents. "The amount of taxes don't have a bearing on market rents," he said. "Market rents are driven by supply and demand." Foley added that the rental companies generally absorb the property tax increases as part of their operating costs. According to the Fairfax County Office of Management and Budget, assessments for apartment buildings increased 3.54 percent in 2001, 9.53 percent in 2002 and are expected to increase 9.59 percent in 2003. "Legitimate expenses can be legitimately passed on," said Supervisor Dana Kauffman (D-Lee), a former property manager. As a result of the dearth of affordable housing, about a quarter of all people who receive housing choice vouchers have to return them because they are unable to find a landlord willing to rent to them within the allotted time, said McMahon. Of the 2,067 homeless individuals in Fairfax County, 41 percent of them are employed and roughly the same percentage are children. "If possible we want to stay here but we can't afford it anymore," said Aida Caballo of her Culmore apartment. She said her rent increased $100 over the past year but her husband, a cook, has not seen a corresponding increase in salary. "Anytime you want to rent an apartment you have to think about it twice," she said. "If the rent goes up why don't they raise the salaries?" asked Idalia Pereira, also of the Culmore area. "If I get an increase in my rent, I should have an increase in my salary." Pereira also said that her apartment in the Old Salem complex is infested with rats and cockroaches. "The apartment is too expensive and undermaintenanced," she said. Pereira, whose husband is a roofer and whose three children attend Bailey's elementary and Glasgow middle schools, said she is also trying to move but has found the rents prohibitive everywhere in the county.