“It plays tricks with your memories,” said Ms. Paparo, now 42. “I’ll walk down the street and get a flash. If I lived elsewhere, I wouldn’t have the ghosts of my past jumping into my everyday experiences.”

Her son learned to ride his bike in the same ball field where she learned, and childhood playmates still live nearby. When Ms. Paparo’s mother died last November, neighbors she had known since childhood provided solace.

“The last few months I’ve had a different perspective on it,” she said. “All of a sudden it was really lovely to have that community.”

Yet if you never leave your childhood home, the quirks that irritated you as a child don’t leave either. When Mr. Schaffner was a boy, the kitchen sink gurgled without warning — making a vexing gassy sound that could be stopped only by turning on the faucet. Now, at 29, he finds that bubbling sound still annoys him. Similarly, when Ms. Leitner’s parents visit her at the Seward Park Cooperative, her father moves the sugar back to where he stored it when he owned the place.

Last spring Mr. Schaffner’s fiancée, Offira Gabbay, joined him and his roommate in the Inwood apartment, giving up a cheerful one-bedroom in Brooklyn. The couple had spent months debating which apartment to keep, but there was really never much of a choice. Ms. Gabbay’s rent was $1,272 a month for a 450-square-foot space; Mr. Schaffner’s was less than $1,000 for a three-bedroom.

“New York is increasingly a difficult, hard place to find reasonable housing,” said Arlene F. Boop, a lawyer who specializes in tenant rights. “If you’ve got one version of it, you’re trapped.”

As his 30th birthday approaches, Mr. Schaffner has begun to contemplate the possibility that he might spend the rest of his life in the apartment where his parents were married and where he grew up.

“I’m plenty happy where I am,” he said. “The only reservation that I have is that I never had the choice to go anywhere else .”