A House In Monopoly - When Can I Buy

: You can technically build while another player is moving, though common "gentleman's agreements" suggest waiting until a dice roll is completed.

The official Monopoly rules state that you can buy and erect houses " at any time ". This flexibility is often misunderstood, but as long as you meet specific property requirements, you don't even have to wait for your own turn to start building. Core Requirements for Buying Houses when can i buy a house in monopoly

: You can build between the turns of other players. : You can technically build while another player