SEOUL, South Korea — With his debts mounting and his wages barely enough to cover the interest, Im Hyun-seok decided he needed a new job. The mild-mannered former English tutor joined South Korea’s growing ranks of camera-toting bounty hunters.

Known here sarcastically as paparazzi, people like Mr. Im stalk their prey and capture them on film. But it is not celebrities, politicians or even hardened criminals they pursue. Rather, they roam cities secretly videotaping fellow citizens breaking the law, deliver the evidence to government officials and collect the rewards.

“Some people hate us,” Mr. Im said. “But we’re only doing what the law encourages.”

The opportunities are everywhere: a factory releasing industrial waste into a river, a building owner keeping an emergency exit locked, doctors and lawyers not providing receipts for payment so that they can underreport their taxable income.

Mr. Im’s pet target is people who burn garbage at construction sites, a violation of environmental laws.