Wherever herein petitions, ballots or objections are required to be signed by the owners of property, the following rules shall govern the sufficiency thereof: (1) The signature of the record owner as determined by the records of the county auditor shall be sufficient without the signature of his or her spouse; (2) in the case of mortgaged property, the signature of the mortgagor shall be sufficient; (3) in the case of property purchased on contract the signature of the contract purchaser shall be deemed sufficient; (4) any officer of a corporation owning land in the district duly authorized to execute deeds or encumbrances on behalf of the corporation may sign on behalf of such corporation: PROVIDED, That there shall be attached to the ballot or petition a certified excerpt from the bylaws showing such authority; (5) if any property in the district stands in the name of a deceased person or any person for whom a guardian has been appointed, the signature of the executor, administrator or guardian as the case may be shall be equivalent to the signature of the owner of the property.