6. The receiver may with the approval of the circuit court borrow money against, and encumber, the property as security therefor in such amounts as may be necessary to carry out his or her responsibilities pursuant to sections 441.500 to 441.643 . The circuit court may authorize the receiver to issue receiver's certificates as security against such borrowings, which certificates shall be authorized investments for banks and savings and loan associations, and shall constitute a first lien upon the property and its income and shall be superior to any claims of the receiver and to all prior or subsequent liens and encumbrances except taxes and assessments, and shall be enforceable as provided in subsection 8 of this section.