Builders ask you to make a down payment at the time of booking of the apartment (10-15% of the cost) and another (70-75%) within a couple of months after booking the apartment.
You make the remaining payment at the time you take possession of the flat. This is a highly risky method of making the payments, as you are stuck if the builder delays the construction of your apartment.
You could opt for a construction linked plan where you pay 10-15% of the amount as a down payment and the rest of the payments are made as each level of construction is complete.
You could opt for the flexi plan where 30-40% of the payments are made as a down payment and the rest as each stage of construction is completed.