Five real estate brokers in Northern Virginia with medium-size firms have set up an organization called Realcore that they say is an alternative to national franchising. small real estate brokerage firms, and large, multi-office firms.

The Realcore principals use a photographic display system of houses listed for sale or rent with member brokers. They also administer a training program for agents working for the firms, along with management assistance in bookkeeping, auditing, office procedures and central purchaseing.

"We feel that many of us have been caught between a rock and a hard place," said Robert V. McGrath, president of Carriage House Associates and one of the brokers involved in setting up the organization.

"Our plan is to offer a wide variety of services to medium-size realtor firms at costs which should, because of centralization. save every member broker thousands of dollars in over-head."

Besides McGrath, the brokers include Daniel Macklin of macklin-Hansen in Alexandria and Woodbridge, Fredrick L. Spain of Holley Realty, which has five offices; Dunald Childress, president of Aries Real Estate in McLean (and current president of the Northern Virginia Board of Realtors), and Larry Hargett, bead of a firm with three offices.

McGrath stressed that the Realcore plan is not a franchise and takes no off-the-top cut of the commission fee. He said: "A realtor who elects to join the system elects the programs in which he wishes to participate and pays for those programs by unit of service obtained."

Realcore has set up an office at 8320 Old Courthouse Rd., Vienna. McGrath said Realcore is managing nearly 500 rental and business properties for the five founding members under the direction of Diane Miller. She moved from the Macklin-Hansen office to direct Realcore Management Inc., a division of Realcore Services Inc.