Section 18. The spouse of a person incapacitated by reason of mental illness desiring to convey said person’s real estate absolutely or by mortgage may file a petition in the probate court describing such real estate and praying that homestead therein may be released and stating the facts and reasons why the prayer of the petition should be granted. The court, after notice and a hearing, may by decree, authorize the guardian of the person incapacitated by reason of mental illness to make the release by joining in any deed or deeds, mortgage or mortgages of the whole or a part of said real estate which is or are made within five years after said decree by the spouse of the person incapacitated by reason of mental illness or by a trustee for such spouse.