The district may purchase transit equipment, such as cars, trolley buses and motorbuses, or rolling equipment, and may execute agreements, leases, and equipment trust certificates in the forms customarily used by private corporations engaged in the transit business appropriate to effect the purchase and leasing of transit equipment, and may dispose of the equipment trust certificates on terms and conditions that the board may deem appropriate. Payment for the equipment, or rentals therefor, may be made in installments. The deferred installments may be evidenced by equipment trust certificates payable from any source of funds specified in the certificates that are or will be legally available to the district. Title to the equipment shall not vest in the district until the equipment trust certificates are paid.