A city or town may, in anticipation of the acquisition of a site and the construction of a building, execute a lease, as lessee, prior to the actual acquisition of a site and the construction of a building, but the lease shall not require payment of rental by the lessee until the building is ready for occupancy. The lessor shall furnish a bond satisfactory to the lessee conditioned on the delivery of possession of the completed building to the lessee city or town at the time prescribed in the lease, unavoidable delay excepted. The lease shall provide that no part of the cost of construction of the building shall ever become an obligation of the lessee city or town.