“Many of these buildings were built or converted in the 1980s, and are largely made up of smaller apartments, such as studios and one-bedrooms,” said Jonathan J. Miller, the president of the appraisal firm Miller Samuel. “The smaller the apartments, and the more smaller apartments there are, generally the higher the pied-à-terre factor.”

And perhaps surprisingly, the data indicated that “the vast majority of pieds-à-terre are middle class,” Mr. Miller said. “They are owned by people who have a studio in the city and a home in the suburbs, or maybe it was their first apartment that they chose to keep and rent it out.”

That’s what Swarna Kuruganti did. In January 2008, she bought an apartment at Madison Green, a towering complex at 5 East 22nd Street. The 424-unit building is a block from Madison Square Park, and the subway is just steps from the front door.

Image CitySpire, at 150 West 56th Street, is one of the least occupied buildings in Manhattan. Credit Joshua Bright for The New York Times

“I had been looking to buy for several years and had built up savings, and even though it was the peak of the real estate market, I signed the deal,” said Ms. Kuruganti, who purchased a one-bedroom on the 26th floor, with views of the Empire State Building.

At the time, Ms. Kuruganti was single and working as a management consultant, which involved a lot of travel. “I wasn’t really home other than two or three months a year,” she said. “I would come home on the weekends, but on Monday morning I would be back on the plane.” She knew her neighbors well enough to say hello as they passed in the hall, “but these high-rises are like mini cities, with so many apartments and so many people. It is like a world unto its own,” she said.

After three years of living at Madison Green, Ms. Kuruganti met the man who became her husband, and they moved to Bloomfield, N.J. She debated selling the apartment, but “it was my first real estate investment, and all the people I talked to swore it was a good investment and told me I should keep it.” So Ms. Kuruganti, who is a founder of the start-up Wellwatch.co, began renting it out.

“The monthlies are low, partly because the building has so many apartments, and it is a great location, very central,” said Nathaniel Faust, the associate broker at Citi Habitats who helped Ms. Kuruganti find her current tenants, who pay $4,500 a month in rent. “Since the common charges and real estate taxes are low, Swarna can cover her monthlies and then some with the rent, so it is doing very well for her.”