This is a mortgage, not a secret contact. The word "mortgage" is a Cantonese transliteration of the English word "mortgage", which refers to obtaining a bank loan with real estate and other physical assets or securities or contracts as collateral, and repaying the principal and interest in installments according to the contract. After the loan is paid off, the bank returns the collateral.

The down payment is the first payment paid to the seller at the same time when signing the sales contract.

56# is 56.