Section 16. If a person by reason of mental weakness is unable to properly care for his property, the probate court may, upon his petition or upon the petition of one or more of his friends, or if a person by reason of physical incapacity is unable to properly care for his property the probate court may, upon his petition or with his written assent, and in each case if after notice as provided in section seventeen and after hearing it appears that such person is incapable of properly caring for his property, appoint a conservator to have charge and management of his property, subject to the direction of the court.