A Brooklyn real estate developer allegedly vanished with over $4 million of his clients’ money — putting the group of 20 Asian immigrant families at risk of being booted from their homes, The Post has learned.

The families had entrusted developer Xi Hui “Steven” Wu with tens to hundreds of thousands of dollars each in deposits to buy condos at their Bay Ridge residential building, located at 345 Ovington Ave., according to court papers and their lawyer.

But Wu allegedly disappeared without giving the residents ownership titles to their units — because as it turns out, he didn’t actually have permission from New York state to sell condos in the building, lawsuits brought by the families allege.

“It’s definitely devastating for us,” said Chin How “Rei” Tan, who told The Post he paid Wu $187,000 for the condo where his 88-year-old father and 80-year-old mother have been living since 2015.

“It will be terrible,” Tan, 47, said of his parents potentially being forced to move out. “[They] were supposed to be here hopefully for another 30 years.”

“Where are they going to be staying?” Tan asked. “It was supposed to be the apartment they retired in.”

In addition to the cash for the condo — half of the total cost of the unit Wu was selling — Tan said the family also paid $7,000 in what the developer claimed were condo fees.

Edward Cuccia, an attorney representing the families, told The Post that Wu “ran a massive scam where he cheated over 20 immigrant families not only of their life savings but also of their hopes and dreams of owning a home.”

“Now these families are facing eviction and total loss,” Cuccia said. “This is the most egregious case of real estate fraud I have ever seen in my over 30 years of practicing law.”

Wu began attracting buyers in 2012, collecting amounts ranging from tens of thousands to upwards of $500,000 from each family as deposits on their homes — and promising to give them the title for the units, court documents allege.

He pocketed various percentages of deposits from residents — and even took the full amount of the cost of the home from a few families, according to Cuccia.

Wu never delivered on transferring ownership to the residents — who had moved into the building in the meantime — as he wasn’t permitted by the state to sell condos in the building, the lawsuits claim.

Instead, he stopped payments on a $6 million loan he took out to build the apartments — and ran off with the deposits, Cuccia claims.

In May, the residents won judgments against Wu for the money they paid him.

But their future is still uncertain, since lender Maxim Credit Group, LLC foreclosed on the building — leaving the residents open to be evicted down the line, Cuccia said.

The building goes up for auction on July 28 and after that, the new owner could initiate eviction proceedings against the residents, the attorney explained.

“We didn’t bring it upon ourselves,” Tan told The Post. “The developer, Steve Wu, he should be responsible.”

Tan said he hopes they can work something out so that the residents can continue living in the building.

Ka Cheng “Kris” Chan said her mother, Cheng Peng Chu, 60, paid Wu $200,000 — her life savings — for her apartment that she moved into in 2014.

“She is very angry,” Chan said of her mom, who works as a server at a restaurant and immigrated to the US roughly 10 years ago. “We all know [Wu] in the neighborhood. How could he do that to us?”

“We feel he actually betrayed us. He just walked out from the project,” said Chan, who until recently lived in the apartment with her mom.

The residents will be meeting with local politicians on Wednesday to try to bring attention to and gain support for their situation in hopes of halting their potential eviction.

Lawyers for Maxim Credit Group, Wu and Wu’s lawyers did not return requests for comment.