A Builder/Buyer (Buyer Seller) Agreement is an important document while transecting to buy a property. This agreement holds all the clauses, terms and conditions and legal implications, for the buyer and the developer, should there be a default from the either sides. A builder-buyer agreement will contain all the clauses that are essential for the construction of the flat including the fixation of carpet area, The time frame of the project
The payments terms and clauses, Interests, penalty, default charges for a buyer Approvals, sanctions, obtained by the developer to undertake the development, Approved layout plans and drawings of the project, Title and ownership of the project, Is the development being out sourced, Is the land clear of loans / mortgages, where the developer proposes to undertake the development, etc.
Therefore you can obtain the attested or certified copy of the BBA and RWA, if the BBA has been registered you can get a certified copy for the registrar's office itself.
You should take a legal opinion from your own lawyer before venturing into the purchase if you find some discrepancy anywhere.