As the soon-to-be first family sat down in Florida for their Thanksgiving feast, they were watched over by the core part of their new extended family — a contingent of at least 150 Secret Service personnel.

And when Donald Trump gets sworn in as president on Jan. 20, that contingent will balloon to more than 920 Secret Service agents and support personnel in Washington and his hometown, New York.



The price tag for all that security is already very big, or as the Manhattan mogul might put it, "Yuge," internal Homeland Security and Secret Service documents reviewed by NBC News show.



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Right now, the cost to taxpayers is more than $2 million a day, the documents show, a number that is sure to increase whenever the president or the first lady travels — or when the threat level rises.



Meanwhile, the New York Police Department is already handling external security at Trump Tower, the president-elect's Manhattan home base, at an estimated cost of $1 million per day.



"You put a price tag on anything around the president, then you're putting a price tag on his life, and that is priceless," Jonathan Wackrow, a former Secret Service agent who has protected every living president, including Barack Obama, told NBC News in an exclusive interview.



Protecting Trump's family presents unprecedented challenges. First off, it's a big family — 18 members in all, including Melania Trump and her 10-year-old son, Barron, as well as four adult children, three of them married, with a combined eight grandchildren.



The Secret Service has not had to protect the adult children of a president-elect in a long time, Wackrow said.



Also complicating security arrangements is Melania Trump's decision to stay in Manhattan until Barron is done with school in June. Donald Trump has told his team that he intends to make regular weekend trips home to Trump Tower until his wife moves into the White House.

So millions of dollars worth of infrastructure will have to be installed in Trump Tower to turn it into a White House North.



"You have to be able to conduct a global war from the front porch — that is just the reality of the situation," said Terry Sullivan of the White House Transition Project, a nonpartisan organization that helps prepare the staffs of incoming presidents for the rigors of working in the White House.



When Trump heads home to the luxury 58-story high rise on Fifth Avenue, the feds will also need to find accommodations for staffers in a building where a modest one-bedroom, one-bathroom apartment rents for $5,250 a month, according to the StreetEasy real estate site.



"They would need at least a whole floor, and every apartment on that floor would need to be turned into an office," Sullivan said.



New York Mayor Bill de Blasio is so concerned about the city's getting stuck with the bill that he's already been in touch with outgoing Homeland Security Secretary Jeh Johnson, as well as with the president-elect's transition team, to ensure that the feds guarantee reimbursement.



"I made clear to [Johnson] how committed we are to the president-elect's security, but I've also made clear to him that there's extraordinary costs involved and that we want to start the process of understanding what kind of federal reimbursement we can get," the mayor said recently. "I will be speaking to the president-elect's team as early as next week on this topic."

Former Secret Service agent Evy Poumpouras, who was part of the security details that protected Obama and President George W. Bush, said she hopes Trump will reconsider at least his own weekend plans once he becomes president.



"This is one of those situations where they really should have an honest conversation with him and just really explain to him that this is not a good idea," she told NBC's Brian Williams. "To physically re-create the security that exists at the White House in New York City, it's not going to happen."



She added: "There's buses going by. There's trucks going by. When that detonates, that building is not going to withstand that blast."



In a subsequent interview with NBC News, Poumpouras said that flights out of LaGuardia Airport would have to be rerouted so they didn't fly directly over Trump Tower and that the subways running below the building would have to be fortified and closely watched.

"Routes will need to change," she said. "All the security changes to make this happen will cost millions upon millions."



Then there's presidential gridlock. Any time the commander-in-chief ventures in and out of New York City, traffic grinds to a halt, and commuter chaos ensues.



Three days after he was elected, Trump's motorcade forced the shutdown of the Lincoln Tunnel — a key artery connecting New York City to New Jersey — for 60 minutes at the height of the evening rush hour.

Back in 2009, there was gridlock across Manhattan when the Obamas flew in one Saturday for dinner and a Broadway show. And while the first couple has been back home to Chicago numerous times in the eight years they've been in the Washington, they've spent only 14 nights in their Hyde Park home, according to White House records.



For a taste of things to come, consider how Trump arrived Tuesday evening at Mar-a-Lago, his 126-room, 110,000-square-foot mansion in exclusive Palm Beach, Florida, for the Thanksgiving holiday. It was in a 45-vehicle convoy that included limousines, vans — and an ambulance.



Trump's glamorous Florida getaway will also get a bit of a makeover.

"It is the case that the Secret Service regularly upgrades a president's off-campus residence," Sullivan said. "Typically, it includes security apparatus and global communications."



Trump will have to get used to having lots of unfamiliar faces around him all of the time.



"Just think about you at your home tonight and four strangers just show up and they're standing in your kitchen," Wackrow, the former agent, told NBC News.



"Secret Service protection is the most intrusive thing that anyone could ever experience. We experience parts of your life, but we're also there in those private times when things aren't good — family arguments, family loss. We're there when staff goes away and the military goes away. The only ones left are the Secret Service agents. We're there 24 hours a day, 365 days a year."



That takes some getting used to.



For example, Obama was told early in his administration that his protective detail needed four hours' notice to safely manage his pickup basketball games. That, at first, did not go over well.

"It takes a little bit of time, and it takes a little bit of give and take on both sides," Wackrow said. He said that the Secret Service will "need to understand [what] is unique about protecting Donald Trump and the first lady."



"If the president-elect says, 'No,' there's going to be a conversation," Wackrow added. "We're not going to just say OK. We're going to actually push back. We may have to modify, but we'll understand what that pressure point is and then work around it."



The Trumps' trip to Florida wound up being a compromise on both sides, a Homeland Security official familiar with the operation told NBC News.



The cost to U.S. taxpayers? Seven million dollars, the official said.

