But never mind photos of adults posing triumphantly with empty beer bottles or wearing underpants as hats: Brokers say some of the most eyebrow-raising online tidbits can involve children.

“Kids are really where you find a lot of the information that can cause some concerns,” said Steven O. Goldschmidt, a senior vice president of the Warburg Marketing Group of Warburg Realty, and a member of his Morningside Heights co-op board. “There have been one or two incidents when we looked at an application and then looked at the children. They were wild to the nth degree.”

In one case, he said, the applicants had a 16-year-old son. An online search found photos of him in full Goth regalia. That didn’t go over well with the board. Worse, the page contained “some language and referred to parties and to drug use in a manner that caused some concern,” Mr. Goldschmidt said. After the board raised questions, the family pulled its application.

Sometimes Internet sleuthing can work in the buyer’s favor. Shari Bornstein and Bryan Meccariello of Southington, Conn., recently sought to buy a one-bedroom in a small Upper West Side co-op building. Their plan was to turn it into a pied-à-terre.

The board was worried: No one in the building had ever used an apartment as an occasional residence. And the couple had a teenage son, Garrett. Would he be coming there  by himself?

When the couple showed up for their interview, the member who served as a spokeswoman for the board took them aside and told them not to worry, she had checked out the boy online and thought he was terrific, said Ms. Bornstein and the two agents who represented her, Holly Palance and Jennifer Roberts of Halstead.

Image Steven O. Goldschmidt says social networks provide his co-op with applicant information, pro and con. Credit... Jennifer S. Altman for The New York Times

Indeed, a Google search of young Garrett’s name yielded, among other things, a Facebook page for a hot-dog stand he runs and a local news report about a pedicab business he started. In the segment, he said he wasn’t in it for the money, but to provide a service for Southington residents.