Stephen Kotler, executive vice president of the division, said he expected business to increase by 15 percent again this year, based on the requests he has already received from banks, consumer-products companies and media firms. Even though his clients can afford high rents, he said, they do not have many choices.

“There’s going to be limited inventory and a lot of demand,” Mr. Kotler said. “There just hasn’t been enough rental product built,” he said, as, developers have said that the price of land and the costs of construction in the last few years have made it impractical to build rental buildings. They have instead focused on condominiums.

Renters without high salaries have not been shut out of the market. They are squeezing in extra roommates or making alterations as never before much to the frustration of landlords. The rents for one-bedroom apartments in Manhattan average $2,567 a month, and two-bedrooms average $3,854 a month, according to data from Citi Habitats, a large rental brokerage company, but rents tend to be far higher in coveted neighborhoods like the Upper West Side and TriBeCa.

Because landlords typically require renters to earn 40 times their monthly rent in annual income, renters of those average apartments would need to earn at least $102,680, individually or combined, to qualify for a one-bedroom and $154,160 to afford a two-bedroom.

Young people making a fraction of those salaries are doubling up in small spaces and creating housing code violations, said Jamie Heiberger-Jacobsen, a real estate lawyer with her own practice. She is representing landlords in 26 cases that claim overcrowding or illegal alterations in elevator buildings in Murray Hill, the Upper East and Upper West Sides and the Lower East Side. A year ago, she handled a half-dozen such cases.

Ms. Heiberger-Jacobsen said she was seeing the overcrowding not only in tenement-type buildings, but also in doorman buildings. “It really does create fire hazards,” she said. “You can’t just have beds all over the place.”

But more renters are finding that they cannot afford to stay in the city without resorting to less conventional living arrangements. For the last five years, Mindy Abovitz, 27, a drummer and graphic designer, has been living with four roommates in a 1,500-square-foot loft with one bathroom in Williamsburg, Brooklyn, which has become a haven for young people, that rents for $2,600 a month.