I want to ask if there is a rental room in the family building.

Pay attention to manners first, and then express your needs to each other. If you want to find out if there is a rental house in your family building, you should first pay attention to politeness and not be too impatient, and then express your needs to the other party. For example, you can say hello, and I want to ask if there is a rental house in the family building. If you have, you can contact me at any time.