Okla. Stat. tit. 18 § 550
Any such charitable or educational corporation may borrow money and incur debts either for its principal purposes, or for the furtherance of any or all its business enterprises or both. In case money is borrowed to aid any corporation, a majority of whose stock is lawfully owned by such charitable or educational corporation, it may loan or advance the same to such controlled corporation on such terms as may seem advisable to its trustees. Any such charitable or educational corporation so borrowing money to aid any other corporation as aforesaid, may evidence its indebtedness by notes or bonds and secure their payment by mortgaging and pledging all or any part of its property, real, personal and mixed, except the real estate, buildings and personal property consisting of household goods, farm implements and domestic animals used for the ordinary conduct and operation of the institution of such corporations, which last-named property shall never be liable, or in any manner taken for indebtedness, charge or lien of any nature whatsoever contracted by such corporation, to aid another corporation as aforesaid, provided that if any charitable or educational corporation shall maintain or carry on any auxiliary business under the terms of Section 549 of this title, either directly or through any other corporation or corporations, such fact shall be held to be an agreement on its part and on the part of such other corporation or corporations that all property owned by, devoted to, or used in such auxiliary business hereunder, shall be subject to taxation for all purposes in the same manner as taxable property generally and that such property shall not be exempt from taxation by reason of the fact that the revenues or profits or a portion thereof, are used or intended to be used as additional funds for carrying out the charitable or educational purposes of such corporation or for reinvestment by or in behalf of such charitable or educational corporation; and it is hereby declared that no such property shall be exempt from taxation; and provided, further, that the real estate, buildings, and personal property consisting of household goods, farming implements and domestic animals necessary for the ordinary conduct and operation of such charitable or educational corporations, shall be exempt from taxation.
Okla. Stat. tit. 18, § 550