Revenue Recognition;

Dear Sir, I would like to get your guidance on revenue recognition in the following scenario; An entity sells land to its customers over a period of time. A customers is allocated a piece of land once they pay an initial deposit amount then the balance is expected to be over a period of time based on an agreed written payment schedule. The customer only takes control of the land when their obligation with the customer is fully paid up. At what point is revenue recognised? Note; The balance is expected to be paid on a monthly basis.