1. There are two ways to buy such flats. One is by getting a tripartite agreement signed by the builder, the seller and you wherein you pay the consideration to the seller and the builder accepts you as the substituted buyer. Big builders refuse to enter in to such tripartite agreements,
2. In the second method, the 1st buyer apllies to the builder for substituting your name in place of his name as the buyer and the builder issues fresh allotment letter (of the flat) cancelling the one already issued to the 1st owner after collecting fees for the same which is generally in between 1 to 3% of the cost though this is not mandatory,
3. Once you get the re-allotment letter for the said flat, you step in to the shoes of the 1st allottee/buyer and act as the buyer.