ON a patch of sand 50 yards from the United States border, Mexicans Mauricio and Lupe Espinosa are building their dream house.
With a view of huge multilevel houses sprouting on the rocky mountainsides of El Paso, Texas, in the distance, the Espinosas are hammering together a dozen wooden pallets to create the 10-foot-by-12-foot, one-room space they will call home. When the frame is completed, they'll cover it with cardboard - tarpaper when they can afford it - and will then tap in to a pirated electric line running haphazardly across the desert floor for light. There will be no running water.
''This will be a step up for us,'' says Mr. Espinosa, his two young sons grinning from atop a pile of unused pallets. ''We pay 350 pesos [about $48] a month rent where we live now, but once we're in here it will be free, so we'll be better off.''
The Espinosas are part of the booming population of Anapra, a dusty slum on the western fringe of the large industrial city of Ciudad Juarez, Mexico. In recent years Anapra has grown to a population of about 10,000, its unpaved, sewerless streets swelled by Mexicans drawn to two things: jobs in Juarez's expanding maquiladora industry and the economic opportunities offered by the adjacent border. Maquiladoras are American and multinational manufacturing plants that are cropping up in Mexico to take advantage of cheaper labor costs and access to US markets.
Now, concerned about the flood of illegal immigrants and drugs coming across from Mexico, the United States is closing off the once relatively porous border. Since 1993, the Border Patrol has posted agents around the clock on the border separating Anapra from Sunland Park, N.M., as part of an El Paso border operation dubbed ''Hold the Line.'' A 1.3-mile, 10-foot-high fence is being built to further stanch illegal crossings.
The Border Patrol says the fence is necessary to help stop illegal immigration, but more important to curtail the criminal activity that has preyed on the US side of the Anapra border. The majority of El Pasoans, who have already seen crime drop with implementation of Hold the Line, support the fence construction.
But the fence will further disrupt an informal, cross-border community that has developed over years of daily unofficial border crossings that were not perceived as illegal so much as simply convenient.
Espinosa has already felt the effect of a change that has him looking less across the border and more to Juarez for his family's well-being. In the past, he could count on crossing into El Paso for small jobs - washing cars, painting, or gardening. But unable to depend on access to that work, he recently took a job in a Juarez gas-tubing plant.
''The problem for me is that I earned in a day over there'' - about $20 - ''what I earn in a week here,'' he says.
''I call it our double crisis,'' says Jesus Ruiz Herrera, who runs a butcher counter in one of Anapra's grocery stores. ''We have the devaluation [of the peso] over here, and that's when they decide to put up a fence over there. It's made things doubly hard.''
Stories like the Espinosas' are common in Anapra. Sergio Torres and Marta Castillo Torres live with their nine children in a cinder-block house in an older section of the sprawling neighborhood. Mr. Torres still tries to cross the border daily to the various odd jobs he has established in El Paso over several years, but he succeeds less frequently. As a result the family depends more on Mrs. Castillo Torres's job in a clothing-assembly maquiladora, where she earns 120 pesos [about $16] a week.
''If they make it any harder for us to cross, it will be a disaster for the people here,'' Mr. Torres says.
Those are familiar words to Kathleen Staudt, a political scientist at the University of Texas El Paso, who has studied the El Paso-Juarez economy for several years. Her work shows that at least one-third of households on both sides of the border benefit economically from a more open border.
''People here had access to lower-cost services over there, while people from Juarez found jobs here or bought products at a lower price here to sell at a profit there,'' Ms. Staudt says. ''The opportunities were especially important for lower-income families.''
But low-income earners are also the least likely to have border-crossing cards or to succeed in obtaining them. US officials want to be sure an applicant for a crossing card is established in Mexico, so they require such documents as electricity bills and credit-card bills before issuing a card.
Such requirements bring a bitter laugh from Anapra residents, who have few if any services to be billed for, and who consider credit cards exotic.
''I tried getting one of those cards,'' Mr. Torres says, ''but it's impossible.''
Other Anapra residents have dismissed the idea of gaining any economic benefit from the opportunities the border might offer and have accepted that their future, for better or worse, lies in Mexico.
''We never go to the other side [of the border] anyway, so I don't think this new wall is going to make any difference in our lives,'' Esther Martinez says. The mother of five is proud to show off the new one-room, cement-floored house her husband's $22-a-week janitorial job in Juarez has made possible.
Critics of stepped-up American efforts to close the border say the consequences, in terms of a poorer neighbor to the south, will prove a bigger problem in the long run.
''Everyone is talking about a global economy, but they don't want that to mean any free movement of people or equal economic opportunity,'' says Ruben Garcia, director of a Roman Catholic Church-sponsored migrant shelter in El Paso and a lifelong border observer. ''The philosophy is 'I'm fine, you're foreign and don't matter,' and the border serves as a justification for that thinking.''
Mr. Garcia recalls a recent local television news report on illegal immigrants who give birth in local hospitals. ''They talked about the sucking sound of draining tax dollars, as each birth cost taxpayers $1,500,'' he says.
To counter that argument, Garcia says he likes to point out that a handful of maquiladoras in Juarez produces the disposable surgical garments used in that hospital in El Paso and in other American hospitals.
''The workers in those factories earn maybe $20 a week, whereas even at minimum wage here they'd earn $200. So that's a $180 a week subsidy of our medical costs, and if you multiply by maybe 1,000 workers, you start to see how that sucking they talked about is reversed,'' he says.
Espinosa says he doesn't think much about crossing the border or the global economic picture. He is resigned to the difficult turn in cross-border relations.
''If the Americans don't want us, well that's too bad, I'll do something else,'' he says. ''But I do wonder who is going to do all the work they don't like to do.''
Mr. Ruiz, the butcher, has a little different take on things. The worse the situation gets in Anapra, he says, the more pressure will build for people to cross the border for good.
''They can build a fence to the sky,'' he says, ''it's not going to stop people who are desperate.''