NRI wanting to sell a property under mortgage

Hi, Thanks for your time. I have a property with a famous builder in Bangalore. All possession done. All documents clear. Property is not registered, as we recently took possession. We have found a few Buyers. But getting stuck with this four party issues: * Party 1. Buyer - wants to give only Rs. 20 lakhs with the MoU. And Buyer wants the Assignment Form to be signed immediately. And he is also going for a loan with a different Bank * Party 2. Myself (Seller) - Need Rs. 42 lakhs to close the loan. I am only getting Rs. 20 lakhs from Buyer and don't want to put my money to close the bank loan, as I have to transfer a big amount from USA * Party 3. My Bank - Needs 42 lakhs and 10 days to give the NOC * Party 4 Builder (they need Bank NOC to do the Assignment Form) and they need 30 days to execute the Assignment Form Both the Builder and Bank are telling us that, if I sign the Assignment Form with only a Rs. 20 lakh payment, the property will be out of my hands and I run the risk if the remaining payment does not go thru. The Buyer is saying that he does not want to pay a big money upfront, for fear it will get stuck and because we are NRIs and we are in India only for the next 2 weeks. We are willing to make a trip back for signing the Assignment Form. Since there is no "escrow" kind of arrangement in India, how do I structure the agreement and payment terms, so that both parties are at ease. Most of articles I read, say that the Buyer has to pay the amount for closing the Bank Loan, so that the Bank NOC and documents get released....which seems to be the starting point. Thanks and Regards