The Port District shall determine in advance the minimum income that should be produced by the public warehouse or public grain elevator or transportation facilities offered, and if no qualified bid will produce such minimum income, all bids may be rejected and the District shall then readvertise for bids. If after such readvertisement no responsible and satisfactory bid within the terms of the advertisement is received, the Port District may then negotiate a lease for not less than the amount of minimum income so determined. If, after negotiating for a lease as herein provided, it is found necessary to revise the minimum income to be produced by the facilities offered for lease, then the Port District shall again readvertise for bids, as herein provided, before negotiating a lease.