Any waiver of the provisions of sections 325N.10 to 325N.18 is void and unenforceable as contrary to public policy except a consumer may waive the five-day right to cancel provided in section 325N.13 if the property is subject to a foreclosure sale within the five business days, and the owner agrees to waive his or her right to cancel in a handwritten statement signed by all parties holding title to the foreclosed property.