Niles Niami stands on the rooftop of the most expensive house in America, the latest property he has built for billionaires, and considers the best way to describe his design aesthetic. “Badass,” he grins. “Yeah. Badass.”

Sweeping in every direction is a panoramic view of Los Angeles and the Pacific Ocean. Beneath him is a gargantuan glass and marble residence with moats, four swimming pools, 20 bedrooms, a nightclub, a bowling alley, a cinema and walls and ceilings made of jellyfish aquariums. Price: $500m.

From this hilltop eyrie in Bel Air, LA’s plushest neighbourhood, other estates belonging to the likes of Jennifer Aniston and Elon Musk look puny in comparison.

Niami has named this property, which is due to go on the market later this year, The One. Apt, he says, because there is no other like it. “I don’t think it’s cheeky. I think it’s true.”

The construction of this and other so-called giga-mansions underscores a new gilded age in the United States and especially in LA. Tech tycoons and other plutocrats are splashing fortunes for homes breaking records for scale, opulence and excess.

The splurge comes amid a housing shortage that has fuelled a homelessness crisis, with 57,000 people without permanent shelter in LA county, a ragged army that pitches tents on sidewalks and sleeps in cars, doorways and on the beach. The Los Angeles Times columnist Steve Lopez compared the city’s hilltop mansions to giant tombstones marking the death of humility.

A model of Niles Niami’s The One. When completed it will be priced at $500m. Photograph: Dan Tuffs/The Guardian

Niami, interviewed this week at The One and another property called Opus, shrugged off a question about inequality. “You’re asking the wrong guy. I try to provide things that don’t exist to buyers that can afford them.”

For him such properties embody audacity and success. “Anyone who buys one of my homes is making a statement about who they are. These properties reflect LA living at its finest.”

The 50-year-old developer is a showman. He drives a Rolls-Royce and sports a Tom Ford jacket, $2,000 sunglasses and a pearly smile. “Braces and veneers,” he says, tapping a tooth.

The Los Angeles native is self-made, the son of a single mother schoolteacher. “The house I grew up in was as big as some of my bathrooms now.” He started out doing makeup for films and graduated to producing B movies, including a 1998 Steven Seagal flick called The Patriot. When films didn’t make enough money he switched to real estate.

His clients include the rapper Sean Combs, also known as Puff Daddy, and the Winklevoss twins, who minted Bitcoin fortunes.

Niami’s brashness has a touch of Del Boy, the wheeler-dealer in the British TV sitcom Only Fools and Horses whose motto was “who dares wins”. “When I do things I just do ’em,” he says. “Wherever it lands, it lands. You only live once. There is no guarantee of anything in life.”

Niami describes his clients as ‘normal dudes, down to earth … they arrive in a Prius’. But just in case he is throwing in a Bugatti Chiron at his Opus. Photograph: Dan Tuffs/The Guardian

That includes finding buyers. The One, once finished later this year, may be a Xanadu fit for Kubla Khan but if Niami doesn’t get a buyer he risks emulating Ozymandias, another figure from antiquity synonymous not with luxury but hubris and ruin.

Niami is gambling that a billionaire – any billionaire - will find the opportunity irresistible. He bought the lot, which included a 10,000 sq ft house, for $28m in 2012. Six years and lots of bulldozers later a 105,000 sq ft behemoth fills the site. LA has since tightened building regulations so another home on this scale is unlikely.

Size plus panoramic views and interior wonderland will, he hopes, fetch a price that eclipses the $137m paid for a pile in the Hamptons, a US record, and the $300m Saudi Arabia’s crown prince reportedly paid for a French chateau, a world record.

The promotional video is not subtle: a handsome fiftysomething man pulls up in a red Ferrari, strolls past glittering waterfalls and hosts a party where beautiful women throng his VIP booth. “One made for the one,” says the tagline.

Niami’s clients tend to be single men who have made fortunes in tech, finance or oil and own multiple other properties. They apparently would disappoint F Scott Fitzgerald, who declared the rich a different breed. “They just have more cash. They’re normal dudes, down to earth. I want to look bitchin’ and cool but they don’t care, they arrive in a Prius.”

He currently has four other properties at various stages of readiness in or close to Bel Air, Beverly Hills and Holmby Hills, a money zone realtors call the Platinum Triangle.

The Cristal room at Niles Niami’s property The Opus. Photograph: Dan Tuffs/The Guardian

He gave the Guardian a tour of the Opus, a 20,500 sq ft mansion on a cul-de-sac known as Billionaire’s Row.

It went on the market last year for $100m, including Damien Hirst paintings and a luxury car museum. No one bit so Niami excluded the art and the cars and recently dropped the price to $77.5m.

A dream bachelor pad, says Niami. Televisions slide from the ceiling and spin 360 degrees. Instead of “a pantry with tuna cans” there is a Cristal champagne vault. There is a kitchen but he doesn’t expect it to be used. “Anyone living here will go out for dinner. Or maybe order from the chef in the catering kitchen downstairs.”

Niami is seeking investors for other projects in LA and New York. He has ruled out London, beyond financial sanity even for a badass. “I’d love to but it’s too expensive.”