The study by the National Low Income Housing Coalition found that only Nantucket County in Massachusetts and Honolulu County in Hawaii have more expensive rents, based on the federal Department of Housing and Urban Development's annual study of fair market rate rents.
The Low Income Housing Coalition study found that a yearly income of $72,000 is necessary to afford the $1,795 rent for a typical two-bedroom apartment in the county without spending more than 30 percent of income on rent.
Other studies show rents in the county are even higher, according to Kate Comfort Harr, executive director of the nonprofit Human Investment Project (HIP) Housing, which works on providing affordable housing options. "Data recently released by the County of San Mateo cites the average rent for a one-bedroom apartment in San Mateo County as $1,925 a month, putting it out of reach for most teachers, home health aides, bank tellers and so many others," said Ms. Harr.
It would take, she said, 173 hours a week of minimum wage work to afford this rent. "There literally are not enough hours in the week," she said.
Ms. Harr said the situation has been made worse by the extremely low number of affordable housing units and the loss of redevelopment agencies, which had been one of the main sources of funds for affordable housing construction in the county.
HIP Housing, which receives funding from local city and town governments, runs a Home Sharing program that matches those who have space in their homes with those who need an affordable place to live.
Joe Karnicky, a 69-year-old retired engineer who has owned a home in North Fair Oaks since 1978, is currently using HIP Housing to help him find a roommate for the fourth time.
Mr. Karnicky, who has a progressive form of multiple sclerosis and uses a wheelchair, said he likes having someone else living in his home in case he needs an extra hand. He also has an attendant who comes in twice a day to help him in and out of bed.
"It allows me to keep on living here," he said.
His current roommate, who has lived with Mr. Karnicky for seven years, has been able to save enough in rent money during that time to now buy a home in Santa Clarita with his son.
"I'm going to take my time finding a replacement," Mr. Karnicky said.
Mr. Karnicky said he is pleased with the HIP Housing process, which requires both the person seeking a renter and those who want to rent to fill out extensive forms used to match up roommates. "It actually has worked out really well for me," Mr. Karnicky said.
HIP Housing Development Director Clarice Veloso said that rents in the home-sharing program average around $700, creating "a win-win for both home providers and home seekers."
"In the last 6 months, we have seen an 11 percent increase in calls from those in need of an affordable place to live and a 30 percent increase from those at risk of homelessness," said Ms. Comfort Harr.
She said that for every person seeking a renter, there are six people in search of a place to rent, "one of the highest ratios we've ever seen in our program." The program has been in place for 40 years.
According to Ms. Veloso, in the 2012-13 fiscal year, HIP Housing received a total of $25,775 in grant funds from Woodside, Portola Valley, Atherton and Menlo Park. The city of Menlo Park also helped finance an affordable housing project with HIP at 1157-1161 Willow Road.
Visit HIPHousing.org for more information.