“I’m an only child, and my parents like being there for me and helping me,” said Nancy Nie, a graduate student at Columbia whose parents closed late last year on a duplex in Park Slope, Brooklyn, for her and her boyfriend. “They know how hard it is to come by nice places in New York,” Ms. Nie continued, adding that her boyfriend is not thrilled with the arrangement. “He’s very independent and has done everything on his own.”

Mr. Chimon has similarly close ties with his family, “so I guess I knew they would want to help,” he said. “There is that part of me that says it would be nice if I could do it totally on my own. But this is New York; it’s not like I’m the only one.”

Mr. Talwar imagined that some of his friends might be thinking something along the lines of “Oh, your parents bought you a place,” he said. “But I don’t feel like my mother is pulling the strings. And we didn’t look at places that were ridiculous. I told my parents that their first consideration was that it be a good investment.” Soon, he hopes he’ll have the wherewithal to make a similar investment of his own.

Ms. Sanderoff has the same goal now that her father has decided to put her apartment on the market and get out of the landlord business. But “I feel privileged that I was able to have this situation,” she said.

And she’ll miss the ribbing she got when she went home for a visit. “My dad would joke around and say, ‘I’m going to raise your rent next year,’ or ‘If you don’t do this or that, I’m going to raise your rent.’

“The thing is,” she added, “my father never raised my rent.”