Payment terms

I am buying a flat on resale in navi mumbai for 61 Lakh without any bank loan. an mou was made with seller to pay him Rs 18 lakh as part payment, to enable him clear his bank loan. as per mou balance rs 43 lakh is to be paid to seller within one month from date of registering agreement & accordingly same condition is mentioned in agreement for sale. seller is now insisting that this condition should be changed saying that balance amount should be paid through bankers cheque on or before execution of agreement & he is not signing the agreement. what is the solution? his contention is that once the agreement is executed, the original agreement will be with buyer & seller has no protection if buyer does not pay the balance amount, which is not the case if buyer has taken bank loan where original agreement is with bank till loan amount is repaid & hence seller is protected.what is standard condition for paying the balance amount in agreement, if buyer is not taking bank loan. kindly guide. also who should bear service charges of bank for issue of bankers cheque.