1. First of all do not go for any payment unless and until a formal agreement for sale is executed between you and the builder.
2.Tofind out the slab constructions details do ask for sanctioned building plan.If you find that the Municipality has granted permission to construct upto 14 floor then you can for constrcution linked payment olan.
3.However do get the deeds checked by a local lawyer beofre taking the decision.
Good luck.