Subject to the laws of the State, the Council shall have authorization to borrow money in anticipation of the payment of special assessments made for the purpose of defraying the cost of any local improvements, or in anticipation of the payment of any combination of such special assessments, and to issue bonds therefor. Such special assessment bonds may be an obligation of the special assessment district or may be both an obligation of the special assessment district or districts and a general obligation of the City. All collections of each special assessment roll or combination of rolls shall be set apart in a separate fund for the payment of the principal and interest of the bond issued in anticipation of such special assessment and shall be used for no other purpose.