The City Council may provide for the deferred payment of special assessments from persons who, in the opinion of the Council and the Assessor, by reason of hardship, are unable to contribute toward the cost thereof. In all such cases, as a condition to the granting of the deferred payments, the city shall require mortgage security on the real property of the beneficiary payable on or before his or her death, or, in any event, on the sale or transfer of the property.