The purchase and sale contract of the mortgaged house is valid, unless the mortgagor and the mortgagee agree not to transfer it.
 The law stipulates that during the mortgage period, the mortgagor may transfer the mortgaged property. If the mortgagor transfers the mortgaged property, it shall notify the mortgagee in time.
 [Legal basis] According to Article 406 of the Civil Code, the mortgagor can transfer the mortgaged property during the mortgage period. If the parties agree otherwise, such agreement shall prevail. Where the mortgaged property is transferred, the mortgage right shall not be affected.
 Where the mortgagor transfers the mortgaged property, it shall notify the mortgagee in time. The mortgagee can prove that the transfer of the mortgaged property may damage the mortgage right;
 The mortgagor may be requested to pay off the debts in advance or place the proceeds of the transfer in escrow with the mortgagee. The part of the transfer price that exceeds the amount of the creditor's rights shall belong to the mortgagor, and the part that is insufficient shall be paid off by the debtor.