Buying a Resale property, it's under construction and Agreement to sell is registered.

Hi, I'm Buying a Resale property, it's under construction and Agreement to sell is registered by the 1st owner and stamp duty is paid. The 1st owner has bank loan and I've applied in the same bank for loan, I'm told by the bank that loan can be set off as from same bank. The Agreement to Sell has Parking mentioned "Buyer Agrees to Buy Parking as Nil", does that mean Parking is provided/assured. Builder says they will give allotment letter later. How do I assure that I get Parking as promissed by Builder any particular document to ask for after the Agreement to sale. If the Builder and 1st Buyer Agreement mentions that all terms and conditions will apply to the subsequent buyer, should that be included in My Agreement to Sale with the 1st buyer. Also if terms and conditions are mentioned are they enforceable without Builder's sign or in this case do I need to have a tripartite agreement with Builder, 1st Buyer and me. The 1st Buyer and Builder have a delay clause where the 1st buyer will get 12% interest on the amount paid for the delay. The process I'm planning is Token - Done Pre Approval from Bank - Done Agreement for Sale Bank Loan Disbursement Payment to 1st Buyer Sale Deed Is this correct and proper way.