(a) The bonds may be additionally secured by a deed of trust or mortgage lien on part or all of the physical properties of the district and rights appurtenant to those properties, vesting in the trustee power to sell the properties for payment of the indebtedness, power to operate the properties, and all other powers necessary for the further security of the bonds.
(b) The trust indenture, regardless of the existence of the deed of trust or mortgage lien on the properties, may include provisions prescribed by the board for the security of the bonds and the preservation of the trust estate and may make provisions for investment of funds of the district.
(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 them.