Victor Blue for The New York Times

With a soggy cluster of balloons floating beside him, a shaggy-haired demonstrator kept watch on Wednesday inside the front gate of a dilapidated two-story home in East New York, Brooklyn. The residential block was mostly empty, except for a police car idling at the curb.

It was quite the contrast from Tuesday night’s street party as members of the Occupy Wall Street movement moved into the foreclosed house. The goal was to restore the home to a suitable condition so that a needy family could move in.

On Wednesday, the reality of the task was clear: the ceiling was covered in mold, the carpets were mildewed, walls were partially knocked down, and there were a pile of sleeping bags and a beer bottle on the floor.

And so the work began.

“This is not a new occupation for occupiers — this is about the family,” said Max Berger, 26, of Brooklyn. “We’re trying to fix up the home for the family.”

The campaign in Brooklyn is part of a national effort that started on Tuesday in more than 20 states to take over foreclosed houses and turn them over to needy people. The police have taken no action against the occupiers at the house on 702 Vermont Street in Brooklyn, but are there to keep the peace, according to a department spokeswoman.

The property was foreclosed on in 2008 by Countrywide, which was acquired by Bank of America, according to Sean Barry of Vocal-NY, a community organizing group that is working with the Occupy movement. The bank has not issued an eviction notice to force the demonstrators out.

The most daunting challenge, for now, seems the renovation. Construction and architecture experts are evaluating the house, but certain needs are already obvious: running water and electricity, for instance, which Mr. Berger said the group was working to restore. The mold, which he said “is not toxic,” must be removed (he said they were beginning that work on Wednesday), and the mountain of dingy items (like a bed frame and mattress) will need to go.

Eventually, all the work is meant to turn the house into a new home for Tasha Glasgow, 30, her companion and their two young children. Ms. Glasgow said the move would “change everything.” Since her 9-year-old daughter, who has severe autism, was a baby, Ms. Glasgow said she had been in and out of shelters. For the moment she is squatting in an apartment in Far Rockaway, Queens.

She moved into that apartment in 2007, but two years ago the landlord and superintendent left, she said — so now she pays no rent, but lacks water and heat. She added that the building was “falling apart.” Meanwhile, her children’s father is sleeping on his sister’s couch.

“I think the new place will be better, because when I saw it the place wasn’t all that, but people were already fixing it up,” she said of the Vermont Street house.

The demonstrators are trying.

On Wednesday a man wearing a mask was on the first floor breaking up old drywall, preparing to replace it. Wires snaked along the floor so demonstrators could broadcast what was happening in the house online. The live stream was the occupiers’ “only defense,” Mr. Berger said, should the police try to evict them.

Some of the neighbors peeked at the work from their windows.

Joyceleen Burnett, 69, surveyed the scene from her house across the street. She said the occupation attracted media attention to her “quiet neighborhood and this street you never see in the news.”

“The banks need a waking up,” she said. She and her husband, Gladford Bryant, have lived on the block since 1974, and recalled repeated problems with drugs and crime in the vacant building.

“We need the house to be occupied by somebody,” Mr. Bryant said. “Put a decent, nice family there.”