In 2014, Ian Jarvis — along with many of his neighbors at 360 Central Park West — received some unwelcome news. He got a letter from the landlord, Argo Real Estate, informing him that Argo would not be renewing his lease. The building, an elegant prewar rental on the park, was going condo, and he would have to leave.

Mr. Jarvis knew that he’d never find anything remotely like his apartment, a generously proportioned one-bedroom on the 16th floor of the building with a sweeping view of Central Park. At least, he’d never find it for less than $3,000 a month.

He’d moved into the apartment in 2006, after living on the Upper East Side, in a perfectly nice apartment between Park and Madison. But he wasn’t in love with the east side — he’d moved there a few years earlier, after the Los Angeles-based cosmetics company where he’d been a partner was sold, freeing him up to move back to New York — so he reached out to a broker.

“I said, ‘I want to move, but I’m not going down and I’m not going to the side. I’m only going up. Let me know what you can find,’ ” he recalled.