The board of a museum district may by ordinance (i) purchase or lease as lessee real or personal property, or acquire an easement in real property, for public purposes pursuant to contracts or leases which provide that the consideration for the purchase, lease, or easement may be paid in annual installments and (ii) lease as lessee or purchase real or personal property for public purposes pursuant to a lease or purchase agreement which provides that the district may, at its option, purchase the property which is subject to the agreement or lease upon terms providing that payments previously made, or a portion of them, are deducted from the purchase price of the property.
70 ILCS 1105/9