7 CFR 770.7 - Security requirements.
(a) The applicant will take appropriate action to obtain and provide security for the loan.
(1) If a mortgage or deed of trust is to be obtained on trust or restricted land and the applicant's constitution or charter does not specifically authorize mortgage of such land, the mortgage must be authorized by tribal referendum.
(2) All mortgages or deeds of trust on trust or restricted land must be approved by the Department of the Interior.
(c) The Agency may take an assignment of income in lieu of a mortgage or deed of trust provided:
(1) The Agency determines that an assignment of income provides as good or better security; and
(2) Prior approval of the Administrator has been obtained.