Hector Piantini was not sure where he would live when he got kicked out of his home more than six months ago.

With no money and nowhere to go, Piantini found temporary shelter with the Latin-American Youth Center, a Washington nonprofit organization that provides young people with housing.

"This is an opportunity to save money. I want to go to college," said Piantini, 20, who has a job at a local record company and can spend 18 months at the nonprofit group's facility in Northwest.

Yesterday, Piantini joined an estimated 30,000 others on a cool, crisp morning for the 18th annual Fannie Mae Foundation Help the Homeless Walkathon -- a five-kilometer trek, or 3.1 miles, around the Mall to raise money for the homeless.

Although the focus was on helping those who suffer mental illness or addiction and live on the street, there was also an emphasis on people like Piantini, low-income people who are a paycheck away from losing shelter.

The walkathon came just a week after a foundation report showed that about 73,000 low-income households in the District cannot afford their mortgages and rents in a market where last year the average home sold for $450,000. In 2004, a teacher with an annual salary of $52,000 could not afford 83 percent of properties on the market.

"A two-bedroom apartment is $1,200. Families are doubling up and tripling up," said Stacey D. Stewart, president of the Fannie Mae Foundation.

The foundation's mission is to create affordable housing and homeownership, and many of the 178 nonprofits that will benefit from yesterday's fundraiser work toward those goals, Stewart said.

The walkathon, which began with 150 Fannie Mae employees marching through Rock Creek Park and raising $90,000 for four local agencies, was expected to match or exceed last year's $6.5 million total, said Peter Beard, senior vice president of policy and information.

Participants under 25 years old paid $15 to register, while adults paid $25, and traditional pledges were collected by some participants. Corporate sponsors contributed about $2.5 million, Beard said. The foundation also donated $1 for every participant in 600 miniwalks held by churches, schools and community groups the past two months.

People of all ages, from sororities, churches, school organizations and nonprofits, held handmade signs and banners as they marched. Despite the serious subject, the mood was festive, with entertainment from dance and musical groups.

"There's something really empowering about being with 30,000 people," said the Rev. Renata Eustis, pastor of Christ Lutheran Church in Northwest Washington.

Her church contributes to Transitional Housing Corp., a faith-based group that helps homeless families move to permanent housing. "A big component of addressing poverty in this community is affordable housing," Eustis said.

With her hands in the air, Rahima Abdullah, center, shows her excitement as the 3.1-mile walkathon begins on the Mall. About 30,000 people took part in the fundraiser, and nearly 180 nonprofit groups will benefit from it.A bundled-up Kamohni Coleman, 6, snuggles with her uncle, Christopher Peters, as they get ready to start the march.