(a) No mortgage loan or investment therein upon any one parcel of real property shall exceed in amount at the time of acquisition:
(1) seventy-five percent of the fair value of the property if the property is a dwelling house primarily intended for occupancy by one family and the loan is required to be amortized within not more than 25 years by payment of installments thereon at regular intervals not less frequent than every three months; or
(2) sixty-six and two-thirds percent of the fair value of the property in all other cases.
(b) The extent to which a mortgage loan made under paragraph (5) or (6) of section 561 of this title is guaranteed or insured by the Federal Housing Administration or guaranteed by the Administrator of Veterans' Affairs may be deducted before application of the limitations contained in subsection (a) of this section.