The board may invest the money in the retirement fund in real property or improvements thereon or to be constructed thereon when the real property or improvements are acquired or to be made by or for sale or lease to the state or a public agency. The board may acquire the real property under Part 11 (commencing with Section 15850) of Division 3. Title to real property acquired by or on behalf of the board pursuant to this section or under Part 11 (commencing with Section 15850) of Division 3 shall be vested in the board. The Director of General Services on behalf of the state may hire or lease as lessee real property or improvements acquired pursuant to this section for lease to the state. The lease may contain an option or options to purchase the property, or a provision that title to the property shall vest in the state at the expiration of the term, and the Director of General Services is authorized to acquire the property. The board also may invest money in any valid special obligations of the state or a public agency or an agency of either issued to finance a public building and secured solely by the building or revenues, rentals or receipts received from operation of the building. This section shall not be construed as authorization to acquire any real property or improvements thereon or to issue any obligation to finance the acquisition on behalf of the state unless that acquisition is authorized by a separate act or appropriation enacted by the Legislature.