The board of each forest preserve district has the power by ordinance to purchase or lease as lessee real or personal property (including, without limitation, purchases from and leases with other units of local government, school districts, or the federal government or any of its agencies or instrumentalities) for public purposes pursuant to contracts or leases which provide that the consideration for the purchase or lease may be paid in annual installments during the period not to exceed 40 years; to lease as lessee or to purchase real property or personal property for public purposes pursuant to a lease or purchase agreement which may provide that the district may, at its option, purchase the property which is subject to the agreement or lease upon terms wherein payments previously made, or a portion of them, are deducted from the purchase price of the property as provided for in the lease or agreement.
     The maximum amounts that will become due under the terms of the purchase or lease agreements, together with all other indebtedness of the district, however, must be within the constitutional limitations on the incurring of indebtedness for the district and for pertinent public purposes.