765 ILCS 605/3
Whenever the owner or owners in fee simple, or the sole lessee or all lessees of a lease described in item (x) of Section 2, of a parcel intend to submit such property to the provisions of this Act, they shall do so by recording a declaration, duly executed and acknowledged, expressly stating such intent and setting forth the particulars enumerated in Section 4. If the condominium is a leasehold condominium, then every lessor of the lease creating a leasehold interest as described in item (x) of Section 2 shall also execute the declaration and such lease shall be recorded prior to the recording of the declaration.
The execution of a declaration required under this Section by the lessor under a lease as described in item (x) of Section 2 does not make the lessor a developer for purposes of this Act.
765 ILCS 605/3