“It’s a jaw-dropping property,” Billy Rose, president of Beverly Hills-based brokerage Agency, said in an interview. He isn’t affiliated with Niami. “What he’s looking to build will be the everything house on the premier site in L.A.”

The average price of 37 homes sold in the first quarter in the Bel Air-Holmby Hills area of Los Angeles was $5.29 million, down 27 percent from a year earlier, when there were several “super deals,” according to an Agency report.

Spec Homes

New luxury mansions are proliferating in Los Angeles, often without buyers in place, known as building on spec. Niami, whose production credits include “The Patriot,” a 1998 action movie starring Steven Seagal, last September sold a Los Angeles home to entertainer Sean “Diddy” Combs for $40 million.

That was followed by the December sale of a Beverly Hills spec home for $70 million to Markus Persson, who last year sold his video-game company to Microsoft Corp. for $2.5 billion. In January, hedge-fund manager Steven Cohen closed on a Beverly Hills spec home for more than $30 million.

Los Angeles luxury homes have ballooned in size in the past 30 years, said Peter McCoy, contractor for a 53,000-square-foot mansion under construction on a Bel Air hilltop visible from Niami’s project.

“We used to think 18,000 or 20,000 square feet was massive,” said McCoy, who became a builder after working as chief of staff for former First Lady Nancy Reagan. “The guys that are doing spec homes, they’re all sitting there hoping to hit a home run. You’ve got to be a big risk-taker, to like building big homes rather than going to Las Vegas.”

Four Pools

Construction costs for Los Angeles luxury homes average $700 to $800 a square foot before finishings and furniture, McCoy said. Niami, who wouldn’t discuss his sources of funding, has plans that call for four swimming pools, including a 180- foot infinity pool, and about 20,000 square feet of grass as California suffers from a record drought.

“There a lot of things in the house that will help to preserve water,” Paul McClean, the mansion’s architect, said in a telephone interview. “But those are things that correspond with luxury houses, and I can’t tell you that it’s a green and energy-efficient house.”