The Council may enter into installment contracts for the purchase of capital equipment. Each of such contracts shall not extend over a period of greater than ten (10) years nor shall the total amounts payable under such contracts exceed the sum of three (3%) of the gross revenues in any one fiscal year of the City. All such contracts now existing are hereby declared legal and binding obligations of the City. All such deferred payments shall be included in the budget for the year in which the installment is payable.