The Federal National Mortgage Association has made two changes in its conventional mortgage purchase programs to aid older neighborhoods and to broaden home buying in small towns and rural areas.

Conventional mortgages on two-to-four family houses will become eligible for purchase by FNMA Feb. 1. Since the corporation began buying conventional mortgages (those not insured or guaranteed by the government) in 1972, only single-family house mortgages have been purchased.

FNMA chairman Oakley Hunter said: "We expect that this broadening of our conventional program should be especially helpful in urban areas, many of which have a large existing stock of two-to-four-family structures." He added that at least two-thirds of the loans purchased by Fannie Mae would for on properties located in urban areas.

Also, effective Feb. 1, FNMA will permit smaller lending institutions to enter into arrangements with larger lenders who have real estate departments acceptable to FNMA under the requirements of its conventional mortgage programs. The smaller institutions will be permitted to originate mortgage loans for customers in their communities and subsequently sell the loans, through the approved institutions, to Fannie Mae.

In order to qualify to sell mortgages to FNMA, local lenders must maintain certain quality standards in their real estate operations. Smaller financial institutions in towns and rural areas seldom do a sufficient volume of real estate lending to justify the facilities to meet FNMA requirements, Hunter said.

Additionally, face-to-face interviews between borrowers and lenders will no longer be required in outlying areas - but will still be encouraged. When an interview is impractical, the lender now will be permited to take an applicantion by telephone or mail.

Under a federal charter, FNMA operates as a supplemental source of mortgage credit by making funds available to provide a secondary market for home mortgages, conventional and FHA-VA.