SAN JOSE — The young man walked the downtown streets, playing the role of tour guide as he pointed out places where he has spent the night during the past three years. That doorway. Next to this parking garage. Dozing against those trees.

“I always tell people that I’m without a home, but that I’m not homeless,” said Alex, 22, who asked that his last name not be used. “Homeless people are the ones who give up.”

Alex said he hasn’t. But as Bay Area counties report the results of their most recent homeless counts, which for the first time were required by the federal government to focus on identifying young people, a worrisome trend has become apparent: the troubling number of homeless under age 25.

The Santa Clara County census, for instance, found that 17 percent of the total homeless population now consists of young adults and unaccompanied minors. Advocates on the front lines say that’s no surprise considering the brutally high jobless rate among young people — a key contributor to this largely unrecognized problem.

And the fear is today’s youthful, still-optimistic street denizens will spiral into tomorrow’s chronically homeless who become a drain on social services for decades to come.

“There is a growing danger that this could become a lost generation,” said Sparky Harlan, CEO of the Bill Wilson Center in Santa Clara. “We don’t want to have a whole generation of young people who just don’t get off life’s launching pad.”

Until this year, knowing just how many are stalled has been based mostly on anecdotal estimates and scattered statistics about trends in youth homelessness. The educated guess of the National Alliance to End Homelessness is that 550,000 young people nationally go without shelter for longer than one week each year.

But it’s difficult to count people who tend to be invisible. Young people avoid encampments and traditional shelters. They “couch-surf” with friends, sleep in cars, shower at schools. They are so adept at blending in that the California Homeless Youth Project titled a recent report “Hidden in Plain Sight.”

“The dirtiest person in the park might go home to his house, and the cleanest person with the widest smile will have to crash in a sleeping bag,” said Nathaniel, 23, a Redwood City native who did not want his full name used. “That was me. You just never know who is homeless.”

Service-providers say the ranks of young homeless are growing due to a confluence of factors including a lack of jobs, poor funding for programs targeted at youths, and a broken foster-care system.

“I don’t think most of the public understands just how many young people are out there on the streets,” said Bailey DeCarlo, 24, of San Jose, who was homeless for five years. “If you have a home, a family that cares about you, a job, you don’t see it. But the last 10 years have been hard on young people. Just finding a job or going to school is difficult.”

So is keeping a roof over your head. For Alex, and Nathaniel, there was no space at home with large families.

“I was going from the floor to the couch because there wasn’t a lot of room,” said Alex, one of four kids. “It was just too crowded, and I felt like I overstayed my welcome.”

Oakland’s Jarad Andrews and Lovelle, a San Jose native who asked that his last name not be used, had no place to go after aging out of regular foster care at 18. A favorite sleeping spot for Lovelle was an out-of-the-way spot between a wall and escalator inside the San Jose Convention Center.

DeCarlo lost both her parents at a young age, yet still considers herself “one of the lucky ones” because she had friends who let her use their couches and made sure she was eating.

“But I was on the streets part of the time, and that was scary because if you’re a single white female, you always have to be worried about being victimized,” said DeCarlo, who has lived with her grandmother for about five months. “Sometimes I would ride the VTA 22 bus all night long. Most homeless people just call it the Hotel 22. I would ride from Palo Alto, get off at Eastridge Mall for 10 minutes or so, and get on a bus heading back.”

Andrews, 21, is blunt about what it’s like to be homeless.

“It sucks,” said Andrews, who lived in a shelter and occasionally slept in a parking lot and train station before being helped into an apartment by the Oakland-based First Place for Youth. “Having to be outside all the time, nobody wants to live like that.”

Andrews, like all the young people interviewed for this story, somehow has maintained a relatively positive outlook on life. None believes he or she is destined for a future on the streets.

“Most don’t even think of themselves as homeless,” said Deanne Pearn, co-founder of First Place for Youth. “They’re just hanging out. It hasn’t sunk in yet. They don’t identify with adult homeless. It’s almost like they are too early in their homeless career, if you want to call it that.”

The struggling economy has hit young people particularly hard. According to KIDS COUNT, a 2012 report by the Annie E. Casey Foundation, nearly 6.5 million “disconnected youth” between ages 16 and 24 are not in school or the workforce nationally, with 850,000 in California alone. Also, Generation Opportunity, a nonpartisan youth-advocacy group, estimates the unemployment rate for people ages 18 to 29 — when you include those no longer looking for work — is at 16 percent.

For young people without a safety net, the result can be homelessness. That’s what a sampling of local counties has found in the biennial homeless counts for the U.S. Department of Housing and Urban Development.

While some counties have previously counted 18-to-24-year-olds separately, HUD for the first time required all communities to break the group out in this year’s census, which took place in January.

In Santa Clara County, 1,266 unaccompanied minors and young adults younger than 25 were identified — a rise from 762 two years earlier. In San Francisco County, 914 were counted. The number in Contra Costa County was much lower at 201, but even that was a jump from just 44 people in 2011.

In Los Angeles County, 4,863 young people were counted.

“We’re seeing a disproportionate number of kids in all the communities that we survey,” said Peter Connery of Applied Survey Research, which oversaw this year’s assessment in Santa Clara County and eight other California counties. “In some communities it’s more than 20 percent.”

Even those numbers likely underestimate the problem because HUD doesn’t consider someone who is crashing with friends as homeless. But the long-term financial consequences could be devastating, said Dennis Culhane, a professor of social policy at the University of Pennsylvania.

He cites a historical precedent. Researchers have noted a large group of chronically homeless who were born between 1955 and 1965. They were young adults during bad economies and never found a toehold in the job market.

In addition to the personal toll, Culhane said, that older generation probably has led to “tens of billions of dollars in terms of social costs over the years. Now, we have all of the same conditions playing out again due to the Great Recession. This is biggest issue in homelessness today. We just don’t want to repeat that mistake.”

It also would be a mistake to typecast young homeless as problem kids, said Nan Roman, president and CEO of the National Alliance to End Homelessness.

“So often we think they’re homeless because of behavioral issues or they got in trouble with the law,” Roman said. “Often there are behavioral issues, but it’s because they’re upset that their family has just blown up. They were living with mom and then they lost their house and all the kids were just dumped out into the world.”

If there is one positive sign in an otherwise gloomy picture, advocates say, it’s that homelessness usually is temporary for young people. The Bill Wilson Center said 87 percent the young people who stay at its youth shelter eventually leave the streets.

An example of a potential success story is Nathaniel, who was homeless about five years and has just moved into an apartment with the center’s help and is working at Walmart.

“It just clicked for me one day that I didn’t want to live like this,” he said. “I had always thought of myself as being young, living life, having fun. It was like never-never land and I was Peter Pan. But then I realized: ‘Hey, I’m 22.’ I’ve seen the hardship that older homeless are going through, and I don’t want to do that.”

The prospects will be grim for those young people who remain homeless, Connery said.

“It’s sad when you have so many youth getting such a lousy start in life because we’ve learned that the more time you spend on the streets, the worse everything becomes,” he said. “Your health goes down. Your mental health goes down. The chances of becoming a victim of crime goes up. You can’t get a job. Everything just gets worse.”

Alex, who said he has slept all over San Jose, is determined that won’t be his fate. He’s working two jobs and is in a 90-day housing program with EHC LifeBuilders, and he sees it leading to a permanent home.

“I guess I could end up in an encampment if I’m forced to one,” he said. “But I hope not.”

Follow Mark Emmons at Twitter.com/markedwinemmons.