Information is inadequate. Proper advise cannot be delivered without giving a careful reading of the agreement and its content. However, it is advisable that if you're in a position to repay back then repay it back. Also the queriest haven't mentioned what was the actual price of the property, and what part of such property was paid by the potential purchaser. Another thing, in case of repayment please record the same in appropriate papers and also repay back to the actual buyer if he is alive.