The legislative body shall have the power, in its discretion, to determine that the payment of such assessments of fifty dollars ($50) or more may be made in annual installments, in any event not to exceed 10, and that the payment of assessments so deferred shall bear interest on the unpaid balance at a rate to be determined by the legislative body, not to exceed 7 percent per annum. Said interest shall begin to run on the 31st day after the confirmation of the assessments by the legislative body. All such determinations may be expressed by resolution of the legislative body at any time prior to the confirmation of the assessments.