Any special assessment for a public improvement against real property benefitted thereby shall be in proportion to, and shall not exceed, the value of the benefit from the improvement. The Council shall establish the method or methods of apportioning the cost of such improvements among the parcels of benefitted real property. No special assessment shall be levied by the City government against any property in excess of twenty-five percent (25%) of the fair cash market value of the property after giving effect to the benefit accruing thereto from the work or action for which assessed, except where all benefitted property owners waive the above twenty-five percent (25%) limitation and agree to accept on a proportional basis one hundred percent (100%) of the costs of the improvements.