SEOULJang Dae-ik, 27, chief financial officerJang lives in a 356 sq ft studio apartment near Dangsan station in central Seoul. Built in 2013, the flat costs about 120 million won (US$100,500). Jang has given his landlord a 180 million won deposit under Korea’s unique jeonse, or “key money”, leasing system. The lump sum, usually between 50 and 80 per cent of the property’s value, is handed over instead of monthly rent, and the full amount is returned when the tenant moves out, meaning the owner…