For a decade, Park Hyeon-su lived in a windowless micro-apartment in Seoul, working double shifts and saving every penny for a deposit on a nice home. Then real estate scammers took his money.

South Korea's rental housing market features a unique system known as jeonse, in which tenants pay huge deposits — sometimes hundreds of thousands of dollars — then get to live rent-free for years, before getting all their money back when they move out.

The idea is that landlords get access to interest-free cash for speculation, and tenants get free housing, with the property as collateral.