Viewpoint: One HDB flat, two apartments?

Dual-key apartment units are usually associated with private property like condominiums. Recently you might have come across news articles in The Straits Times and The Business Times about HDB flats being turned into dual-unit homes. Is this concept more common than we know of? How can HDB owners do this without getting into trouble? What are the implications to the HDB market?  Brandon Zheng, Division Director at ERA shares his views.See omnystudio.com/listener for privacy information.