As the first government shutdown in seven years got underway on Wednesday, tens of thousands of federal workers face the risk of missing paychecks as broader America braces for the absence of some key services.

Starting on Wednesday, 750,000 federal employees are expected to be furloughed, and essential employees will have to work without pay for the duration of the shutdown, according to the nonpartisan Congressional Budget Office.

The workers will be placed on leave without pay and will get paid retroactively once the shutdown is over.

“The number of furloughed employees could vary because some agencies might furlough more employees the longer a shutdown persists and others might recall some initially furloughed employees,” the CBO said in a statement. 

While Oct. 1 paychecks have already gone out to some 2 million U.S. military troops, they may miss their next payday on the fifteenth of this month if lawmakers can’t reach a compromise to end the shutdown.

Jaime Billert of New York, whose husband serves in the U.S. Coast Guard, told ABC News that she’s already spoken to her children about setting priorities and cutting back on expenses, including dining out.

Billert said she told her children, “Your dad’s not getting paid right now. That’s our sole source of income.”

Other federal employees deemed essential — including Transportation Security Administration (TSA) workers, air traffic control workers and U.S. Border Patrol agents — will be required to continue working without pay.

Jon Zumkehr — a corrections officer at a federal prison in Thomson, Illinois, and president of Local 4070 of the American Federation of Government Employees — said he and his co-workers are concerned about how long the shutdown will last.

The federal government stoppage in December of 2018 lasted 35 days and cost the U.S. economy $11 billion, according to the CBO.

Meanwhile, members of Congress, whose average annual salary is around $174,000, will still collect their paychecks during the shutdown as mandated under Article 1, Section 6 of the Constitution. 

Other impacts of the shutdown could also affect national parks, which remain partially open but could face staff shortages during the shutdown.

In previous government shutdowns, national parks that remained open but unstaffed experienced vandalism and destruction of wildlife habitats, according to a recent letter signed by 40 former park superintendents and sent to Interior Secretary Doug Burgum.

In a statement on its website on Wednesday, the Smithsonian Institution in Washington, D.C., announced that its museums, research centers and the National Zoo will use prior-year funds to remain open to the public during the shutdown at least through Oct. 6.

If the shutdown goes beyond a week, other government services could be cut off.

The U.S. Department of Agriculture’s Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), which assists 7 million low-income mothers and their children, is expected to run out of funding in about a week.

Some key federal agencies are expected to continue running during the shutdown, including the U.S. Postal Service.

Social Security payments are not expected to be affected by the shutdown. Federal financial aid for students is also expected to keep flowing and and student loan payments will still be due, according to the Department of Education.