After losing his job at the U.S. Forest Service, Cameron McKenzie was worried about finding a new job. But first, he had a more immediate concern: How was he going to pay the mortgage?

He’s done the math —finding another job in the environmental sector could take months — and keeping up with the nearly $2,700 monthly payment on his three-bedroom home in Blairstown, N.J., will be a challenge, if not impossible. “Even on unemployment,” said Mr. McKenzie, 27, who worked as a community engagement specialist, “I’m not going to be able to make my mortgage payment.”