How did Ode to Joy know that Fan rented a house?

In the play, Wang Baichuan always thinks that Fan bought the house himself, so he hides the fact of renting a house. However, in the play, Andy met Fan because the house was leaking, but he knew about it.

He followed Andy and Fan into the 19 building. The property downstairs asks who he is looking for, so you can call him. From the property office, I learned that Fan now lives in a rented house of a certain group.

Later, Wang Baichuan telephoned a classmate who was developing in Shanghai. From this classmate's mouth, I am convinced of the fact that Fan does share a house with others now. So Wang Baichuan learned about this problem through the dialogue between fans Mei Sheng and Andy.