When Cynthia Chung, 31, and Jeddy Hao, 32, found their one-bedroom apartment on Craigslist five years ago, it seemed like too good a deal.

Rent was $1,050 a month, a few hundred less than everything else in the area, with no obvious defects to explain the discount. If anything, the apartment was nicer than others they had seen: It was well sized and well maintained, with large windows and a good layout.

Ms. Chung, a wedding photographer, thought they were almost certainly walking into a scam. Mr. Hao, on the other hand, was sure he had discovered a gem. “I had a good feeling about it,” he said.

To Ms. Chung’s surprise, he turned out to be right. Rent stabilization accounted for the lower-than-average rent. If there was any downside, it was that many of their friends lived elsewhere.