Okla. Stat. tit. 58 § 385.1
To obtain an order for mortgaging such real estate for the purpose and under the provisions hereof, the guardian must present a verified petition to the district court or to the judge thereof, setting forth a description of the property, real and personal, on hand and undisposed of, the legally established lien or the obligation which may by operation of law become a lien; the amount of the lien or the amount of the obligation which may by operation of law become a lien, the names and addresses of all parties interested in the estate of the minor, incompetent or mentally ill person, and the specific reasons why it will be to the best interest of the said estate to mortgage, rather than sell such real estate, or a part thereof.
Such authority shall not be given or order made therefor, and no mortgage on any real estate shall be made, given, executed or delivered under the provisions hereof, for an amount in excess of two-thirds (2/3) of the appraised value thereof, as established by an appraisal made by three disinterested citizens of the county within one (1) year of the time of making such order to mortgage.
Okla. Stat. tit. 58, § 385.1