Section 63. A mortgagee, or a mortgage lender or mortgage broker as defined in section one of chapter two hundred and fifty-five E, shall not charge a loan fee, finder's fee, points, so-called, or similar fees in a mortgage transaction involving residential property located in the commonwealth of four or less units and occupied in whole or in part by the mortgagor, except to the extent that such fees or points have been previously disclosed to the mortgagor in writing, which disclosure may be in the form required by section seventeen D of chapter one hundred and eighty-four, or such other form which discloses said fees or points. A mortgagor shall not be obligated to pay fees or points which have not been previously disclosed as required herein. Nothing contained in this section shall limit a mortgagor's ability to obtain from such mortgagee, mortgage lender or mortgage broker a temporary or permanent interest rate buydown.