The Secretary is authorized and directed to require that in connection with any property upon which there is located a dwelling designed principally for a single-family residence or a two-family residence and which is approved for mortgage insurance under section 1709 or 1715e of  this  title  with  respect  to  any  property  or project of a corporation or trust of the character described in paragraph (2) of subsection (a) of section 1715e of this title, or sections 1715k, 1715l, 1715m,¹ 1715x, 1715y, 1715z(i), 1715z–2,¹ or 1750b of this title, the seller or builder or such other person as may be designated by the Secretary shall agree to deliver, prior to the sale of the property, to the person purchasing such dwelling for his own occupancy, a written statement setting forth the amount of the appraised value of the property as determined by the Secretary. This section shall not apply in any case where the mortgage involved was insured or the commitment for such insurance was issued prior to August 2, 1954. Notwithstanding the first sentence of this section, the Secretary is authorized to require, in connection with any mortgage where the mortgage amount is computed on the basis of the Secretary's estimate of the replacement cost of the property, or on the basis of any other estimates of the Secretary, that a written statement setting forth such estimate or estimates, as the case may be, be furnished under this section in lieu of a written statement setting forth the amount of the appraised value of the property.