Queybin Cabrera-Matute, a burly 20-year-old Honduran who arrived in the United States illegally as a child 11 years ago, is hoping his Facebook page might be the ticket to a better life.

He was one of hundreds of young people who lined up last week at the Hyattsville office of CASA of Maryland, an immigrant advocacy organization, to apply for the government’s new deferred-action program, which would allow them to live and work here without fear of deportation.

To qualify, Cabrera-Matute must prove that he has lived in the United States since graduating last year from Friendly High School in Fort Washington. He has no official records to cover the whole 16-month period, but, on his girlfriend’s suggestion, he brought in printouts documenting his casual habit of “checking in” on his Facebook page — from the mall, from Olive Garden. “It just lets all my friends know what I’m doing, in case they want to join.”

That, said a CASA adviser, might be enough to qualify him. Or it might not.

It can be daunting for immigrants in the country illegally to document their lives here. Many have spent years trying not to leave a footprint — working at jobs that pay in cash under the table, or using fake names and Social Security numbers to get work. To qualify for deferred action now, they must try to create a paper trail.

But in some cases, it is unclear what sort of documentation is acceptable, and this has created frustration for applicants and charges from critics that the system will be easy to game.

The confusion stems in part from instructions put out by U.S. Citizenship and Immigration Services stating that, along with things such as bank transactions, utility bills and school records, applicants can send in any “other document you believe is relevant.”

“You can provide copies of anything . . . of course, there’s going to be fraud here,” said Brad Botwin, director of Help Save Maryland, a group opposed to legalization for undocumented immigrants. “They’re never going to show us what documents they accepted, so it’s all smoke and mirrors by Homeland Security.”

Immigrant advocacy groups are also frustrated because they don’t know how to advise applicants on what might be acceptable. Crystal Williams, executive director of the American Immigration Lawyers Association, whose 12,000 members nationwide have been advising clients on deferred action, said her group has been pressing the government for more specifics as to what level of documentation is acceptable.

“We keep putting these questions out and they keep saying, ‘We’re working on it, we’re going to get you answers,’ ” she said. “People still don’t know what works or what doesn’t. People are saying, ‘You go first,’ ‘No, you go first,’ and a few brave souls are going first and everyone’s saying, ‘Okay, who got the approvals, and what did you put in?’ ”

A senior official at the Department of Homeland Security said that the agency has put out an unusually large amount of information about the program, including at 111 meetings with immigrant advocacy groups, but added that “it’s not feasible that we can provide [a list of] the entire universe of documents that would work or not work . . .each case must be looked at individually, based on the facts presented in the individual case.”

Since the government started accepting applications last month, more than 72,000 people have applied, and the first approvals were granted this week, although the average waiting time is expected to be four to six months. Between 890,000 and 1.7 million people are estimated to be eligible.

Officials said they would release the number of approvals and denials thus far within the next few days.

To qualify for the two-year renewable program, applicants must be no older than 30, must have arrived in the United States before age 16 and must have lived here continuously for the past five years.

In showing proof, advocates are telling clients to “be creative,” said Andrea Rodriguez, director of legal services at the Central American Resource Center (CARECEN), a Washington-based Latino community organization. “If you’ve got invitations, if you’ve got photos.”

“You have to look under every rock, regardless of how stupid that rock might be,” said Rex Wingerter, who oversees volunteers at CASA of Maryland, which has been holding clinics to help applicants complete their packages.

Besides meeting residency and entry-date requirements, qualified applicants must be in school or working toward a GED, have graduated from high school or received a GED, or be military veterans in good standing, and they may not have committed felonies or significant misdemeanors.

They must also send in a $465 money order for the government fee. CASA charges $25 for help on the deferred-action applications; private lawyers can charge hundreds, even thousands.

Not everyone has rushed in. Some are waiting to see how it goes for their friends, or the president, said Williams of AILA, whose lawyers have been advising thousands of clients at nearly 100 clinics across the country.

“If Obama loses, people aren’t so sure what’s going to happen to their applications and if they can be used against them,” she said. “And Romney has not offered any assurances.”

Some applicants are considering including evidence that shows them living and working under an assumed name with a fake Social Security number — at the risk of flagging them for law enforcement.

“If you’re going to spend your entire life living under the radar in this country, you have to do things like that,” Williams said.

“We would hope there would be some understanding on the part of the government that, yes, this is a necessary part of living in the shadows,” she said. “It’s the pivotal question here.” She also acknowledged that it would be impossible for the government to provide a list of documents that would cover all situations.

Others are scrambling to apply and then hitting a wall.

“The first time I heard about this I was so excited. I said, ‘Oh, yes! This is my time!,’ ” said Norma, 23, who came to the CASA clinic for advice and did not want to give her last name because she is in the United States illegally. “I’ve been waiting for this for 13 years.”

But after graduating from Gaithersburg High School in 2008, Norma married a U.S. citizen, and their whole life — bank accounts, utility bills, taxes — is under his name.

“I’ve worked as a babysitter, paid in cash,” she said. “And I’ve been taking care of my son.”

It was the second time Norma had come to the clinic, but she and the lawyers there were unable to find anything that would prove she has been here the past four years.

“I don’t know what to do,” she said glumly, adding that she plans to send in her application incomplete — even at the risk of drawing attention to her undocumented status.

“I want to study, I want to go to college and work, but the first thing they always ask me is for my Social Security number,” she said. “I’m not, like, in jail, but I feel like that.”

Sometimes the evidence exists but is tantalizingly out of reach.

Applicants have encountered banks that charge $4 or $5 per monthly statement, or schools that provide only a brief letter rather than the full transcript with the necessary dates, said Sheena Wadhawan, a staff attorney at CASA.

Rodriguez at CARECEN told of a young woman whose family had initially been detained upon entering the United States — an incident that would have been documented, providing necessary proof of her entry date.

“But she is estranged from her parents, and they’re unwilling to give it to her,” Rodriguez said.

Cabrera-Matute, who hopes to study architecture and engineering, must now wait to see if his Facebook habits will help get his application accepted. It if does, “things will be a lot easier, calmer, less nervous,” he said. “I won’t have to walk around thinking something might happen.”