if someone shows up there 3-4 days a week, how would you know? Even China doesn't have the surveillance setup to tell if someone is living in a house or not (well, they can check to see if it is renovated, and can check to see if the lights turn on at night). It isn't really a rule of law society, so you can't use "the trust but sometimes verify system" they used in Vancouver, and it is definitely not like Switzerland where your neighbors are constantly spying on you. It is a bit counter intuitive, but checking on these things is harder in China than in the west.