The giant trucks pumping concrete in Hudson Yards, New York’s biggest real-estate project in a generation, are being financed by an unlikely source: about 1,200 Chinese families in search of U.S. visas.

Developer Related Cos. says it has raised roughly $600 million from the families to build the foundation for three skyscrapers at the West Side project, a 17-million-square-foot colossus of office, retail and residential space set to open over the next decade.

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