The board of supervisors may lease the lot or landing for a term not exceeding five years, the lessee to transact thereat only a general receiving and forwarding business; and, in case of a lease, the board shall fix, with power to alter, a schedule of rates and charges for receiving and forwarding freight, and require of the lessee a bond, payable to the county, in a penalty not less than five hundred dollars as shall be proper, conditioned to observe the terms of the lease and to perform the duties imposed on him by law. The lessee shall keep the schedule of rates conspicuously posted on the premises, and any overcharge shall subject the lessee and his sureties to a penalty of twenty dollars in favor of the party injured. A lease shall not abridge the right of any person to store and forward his own freight at the landing free of charge.