“We weren’t even offering them for rent, but we had a lot of people show up and make rental inquiries,” said Greenburger, whose firm, Time Equities, owns a 33 million-square-foot global portfolio of residential, commercial and industrial real estate.

The company sold five of the seven units, but last summer it rented one for $25,000 a month, a sum that shocked even Greenburger, who has been in the business for nearly 60 years.

“I guess I was surprised because that’s a lot of rent,” the developer said. "But people are interested."

The seventh unit is also for rent—for $35,000 a month.

Faced with a moribund sales market in which high-priced apartments can linger unsold for months or even years, an increasing number of condo developers are becoming landlords and leasing units. They view rental income as a lifeline to cover a project’s debt and other costs, such as property taxes. Renting, they say, will keep them afloat financially in the near term so they can sell the apartments when the market improves.

Try before you buy

Renting is also a way to familiarize potential buyers with an apartment and convince them to eventually make a purchase.

Magnum Real Estate Group is employing the strategy at 100 Barclay St., the former Verizon-owned telecommunications building that the developer converted into 156 ultra-pricey condos. Magnum said that 31 unsold units—almost 20% of the building—are being marketed through a rent-to-own program. According to city records, 42 apartment remain unsold at the property, but Magnum claims that 11 of those are in contract.

On-the-fence buyers essentially can try out an apartment as a rental for at least six months.

Those who choose to buy after six months can credit 75% of the rent they paid toward the purchase, or 50% of the rent from a yearlong lease. Magnum has been asking as much as $24,000 a month for a three-bedroom, four-bathroom unit, according to listings on StreetEasy.

“There’s two different ways of looking at it,” said Jordan Brill, a managing partner at Magnum. “There’s ‘Oh my God, you can’t sell and now you have to rent.’ And the other is that, look, the market is in a state of paralysis, and if you have a good product that can hold its value long term, you can take the risk and do this.”

Brill said Magnum has rented out more than 20 of 100 Barclay’s 31 available apartments in the past six months.

He believes renters, once they get comfortable at the property, will fork over the millions of dollars to stay. Available units are priced from $4.6 million to $12.5 million. The building’s unsold penthouse was pulled from the market after seeking $60 million, then recently reintroduced with a price tag of just under $40 million, a 30% reduction. That unit is not part of the rent-to-own program.

Brill said he couldn’t disclose how many renters have so far decided to buy, but some had.

Central to the new model is the thesis that rich buyers abound. They’re just spooked by the current global epidemic, political instability and a weak market. Many expect prices to continue to fall considering the surplus of available luxury apartments.

“There’s the feeling that the price of newly built, high-end condos may have gone up too far and too fast, and people are skeptical of buying at these prices,” said Nancy Packes, principal of residential consulting firm Nancy Packes Data Services. “So it’s not that we don’t have the people to buy. We never stop minting millionaires and billionaires. It’s [that] no one wants to buy a unit today that they believe is going to devalue tomorrow even if they can afford it. It’s psychology.”

Even a few of the city’s biggest and deepest-pocketed developers have turned to renting. Related has marketed for lease 21 of the 39 units at its disappointing Zaha Hadid–designed condo project at 520 W. 28th St., along the High Line, where sales have flagged.

More recently, the developer quietly has begun to offer at least 11 apartments for rent at the 285-unit 15 Hudson Yards, its recently completed 88-story condo spire on the West Side. Apartments there range from $2 million for a one-bedroom to more than $13 million for a penthouse. Related is asking up to $30,000 a month for a penthouse.

A Related spokesman said the company would not comment, but a knowledgeable source said it is offering apartments both as rentals and through rent-to-own offers at 15 Hudson Yards and 520 W. 28th St.

The company also has seen slow sales at the 143-unit spire 35 Hudson Yards, where apartments are priced as high as $60 million for a penthouse.

Who wins?

Questions abound whether renting represents a financial victory for owners.

Condo projects are most often funded with debt designed to be paid back within months or just a few years as apartments are sold off in rapid succession. Even units that can fetch rents in the tens of thousands of dollars may not generate enough income to pay the sizable debt incurred for their construction or sate the lofty returns investors were expecting.

“You’re going to see this selectively, because not every condo can be a good rental,” said Gary Barnett, founder and chairman of prolific residential development firm Extell, which is offering rent-to-own units at its Lower East Side tower 1 Manhattan Square. “There are a lot of projects where the development costs were so high, you can’t do a rental. To even make a 2% return, you’d need a tremendous rent, and how deep is that market? I don’t know.”

Barnett declined to specify how many units had been rented at the 815-unit glass tower, which was finished last year. He also wouldn't disclose whether Extell is considering rentals elsewhere.

A growing inventory of ultra-high-priced rentals could exhaust demand in that segment of the market, experts say. The deluge isn’t just from developers seeking to convert condos into rentals. Many recent buyers, instead of living in the units, are also putting them up for rent. An analysis by StreetEasy found there are 357 homes in the city with a monthly rent of $15,000 or more currently available.

"There’s always a limited universe of well-heeled, super-rich people, and of course the high-end rental market could become saturated too,” said Donna Olshan, president of residential brokerage firm Olshan Realty. "Developers are doing this because … they need cash flow, but in the meantime the market could fall further. Most developers just need to cut prices. Generally, waiting on the market doesn't get you anything."