The legislative body shall direct the clerk to give notice of the time, place and purpose of the hearing, by mailing written notice to each property owner within the boundaries of the territory sought to be annexed whose name and address appears on the last equalized assessment roll. The clerk shall file, upon the completion of the mailing, an affidavit setting forth the time and manner of the compliance with this section. The notice shall be mailed at least 10 days prior to the date set for hearing.