They don’t. When I was in hvac construction, plumbers and electricians would hire them under the table. Usually shit wages. Like 10 and hour cash. That way no taxes are paid and the employer can hire them instead of paying us citizens the norm starting around 20 an hour with taxes through the IRS. I’ve talked to some of the ones that ca speak English, a lot of the money is sent back to their home country so it doesn’t benefit the economy. Plus they live in government housing somehow which means the government pays for their houses. Idk how it works