(a) District bonds may be additionally secured by a deed of trust or mortgage lien on all or part of the district's physical properties and rights appurtenant to the properties, vesting in the trustee power to sell the properties for payment of the indebtedness, power to operate the properties, and any other power necessary for the further security of the bonds.
(b) The bond trust indenture, regardless of the existence of a deed of trust or mortgage lien on the properties, may:
(1) contain provisions prescribed by the board for the security of the bonds and the preservation of the trust estate; and
(2) make provisions for:
(A) amendment or modification; and
(B) investment of district funds.
(c) A purchaser under a sale under the deed of trust or mortgage lien is the absolute owner of the properties and rights purchased and may maintain and operate the properties.