The Chinese government always have more methods to control whatever they want to control. They can control how many child you are allowed to have, and it is not surprising to see how many houses you can buy.

According to the House Purchase Restriction order:

1. For local residents who already have one apartment, and non-local residents who have been paying tax for two years, they can only purchase another one.
2. For local residents with two or more apartments, or non-local residents with one or more apartments, they are not allowed to buy any houses/apartments.
3. For anyone who buy second apartment, the down payment have to be as high as 60%, and the interest rate has to be 10% higher than average.
4. Tax for transfer of houses purchased less than 5 years are significantly higher.

There are many other restrictions. These are the powerful rules to keep buyers out of the market, and the house market kept flat and down ever since.