Inside the most expensive home in the US, a $250M mansion with a bowling alley, cars and staff

— -- If 924 Bel Air Road in Los Angeles goes for the asking price, it will be the most expensive home in the United States.

At 38,000 square-feet, the home sports 21 bathrooms, 12 bedrooms, a $2 million staircase, over 100 pieces of art, an Italian glass ping-pong table, an 85-foot-long outdoor pool that includes a giant movie screen and a swim-up bar that seats 12 people, a four-lane bowling alley, 300 sets of speakers inside and an additional 150 outside, 17,000 square-feet of entertainment decks outside and 270-degree views of L.A. – not to mention the place comes with $30 million worth of cars.

And the price tag: $250 million.

“I don’t want to take any less,” said developer Bruce Makowsky. “Clearly you have to be a billionaire to buy a house like this. There are 3,000 people in the world that can afford a house like this.”

The house also comes with an operational helicopter pad, through the property doesn’t have clearance yet to land a helicopter there.

And there is more – the house also comes with seven full-time staff members that have been paid for the first two years.

“They’ve all been trained for six months in the house and they stay with the house for two years,” Makowsky said. “You have a great personal chef, masseuse, security, house managers, it’s amazing.”

And if the new owner doesn’t like the house staff, Makowsky said, “I’ll be more than happy to pay for them.”

Makowsky said he financed the whole house himself, without loans or partners.

“There was no budget. Everything had to be absolutely the best,” he said. “When you build quality, anything quality, whether it’s a quality meal, a quality car, a quality home: there’ll always be a customer for it… I just need one.”

Makowsky came out west to retire, but couldn’t resist building some of the most expensive spec homes in the world. This home is his ninth.

“My last home was a guy who had just sold his company for $2.5 billion, I think he was 34 years old,” he said of the 2015 purchase. “[‘Minecraft’ creator] Markus Persson. He came in and said, ‘I just have to have this house.’”

And Persson bought the Beverly Hills mansion for $70 million.

After he sells the $250 million Bel Air home, Makowsky says he has two more projects.

“They will be more expensive and they will be bigger,” he said. “There’s been a tremendous amount of super wealth that’s been generated over the past 10 years… You can sit and look at a big bank account or you can enjoy your life with your money.”

His target buyers are the mega-wealthy, those buying super-yachts.

“The mega-yachts that are out there today, people are spending $250, 300, 350 million, and people are buying a ton of them, globally,” he said. “So what I’m doing is I’m taking that same sensibility and bringing it to homes. It’s never been done before.”

The $250 million home has been on the market for two weeks and Makowsky says he hopes to sell it within 12 weeks.

“I’m not sure how long it’s going to take,” he said. “We’ll see what happens, I’m not sure, that’s part of the fun.”

ABC News' Nick Watt and Lauren Effron contributed to this report.