65 ILCS 5/11-75-2
The lease provided for in Section 11-75-1 by its terms shall specify the purpose for which the leased space may be used. If the purpose is to erect in the space a building above or around a building owned by the municipality, the lease (1) shall contain a reasonably accurate description of the building to be erected and of the manner in which it shall be imposed upon or around the existing building of the municipality, (2) shall contain a provision granting to the lessor municipality the option of renting for municipal use from the lessee any part of the building to be erected and stating the terms upon which this option may be exercised as well as the rent which, after exercise of this option, shall be paid by the municipality, and (3) shall contain a provision granting to the municipality the option to purchase for municipal use the entire building to be erected in the space leased and stating the terms upon which this option may be exercised and the price which shall be paid for the building by the municipality in the event it exercises its option to purchase.
65 ILCS 5/11-75-2