This Division shall be liberally construed and applied to promote its underlying purposes and policies. The underlying purposes and policies of this Division are to: Supplement the Public General Law governing the rental of dwelling units; Encourage landlords and tenants to maintain and improve the quality of housing in this County; Assure fair and equitable relations between landlords and tenants insofar as any rights and remedies granted under this Division are not used by landlords and tenants as a means of harassment; Revise the common law of landlord and tenant to serve more realistically the needs of an urban society developing within the County.