Every lender which engages in the business of making junior lien mortgage loans shall adopt policies and procedures as are appropriate with respect to the maximum amount which, when added to the aggregate amount unpaid upon all prior mortgages, liens, and other encumbrances of record upon the real property or shares (in the case of a cooperative apartment unit), the lender shall advance pursuant to a junior mortgage loan. Such policies and procedures shall be subject to the superintendent's periodic review.