At least two private companies say they are preparing to take on the National Association of Realtors's near-monopoly on the business of identifying homes for sale.

The two firms plan to launch alternatives to the multiple-listing services run by local NAR members serving on local Realtor boards. A multiple-listing service (MLS) is a database that lists homes for sale and provides detailed information about each.

More than 90 percent of multiple-listing services nationwide are run by local Realtor boards, according to the National Association of Realtors.

Jerry Jaros, the association's senior vice president, said 700 to 750 local boards operate the MLS system serving their areas, while about 50 others, including those in Portland, Ore., Pittsburgh and Harrisburg, Pa., are privately owned.

Breaking the Realtors's hold on the MLS business, the private challengers contend, will give home buyers access to a greater selection of homes while providing sellers with exposure to a wider buying audience.

Supporters of the system, however, counter that the private systems could actually limit consumer choices by concentrating market power into too few hands.

Few, if any, private multiple-listing services have broken into the business in the past decade, but two companies said they plan to do so this year. And, in a further departure from the status quo, both aspire to eventually create nationwide MLS information networks that could help buyers moving between cities to initially screen possible home purchases from afar.

Within the next few months, Dallas-based American Financial Network said it will test its M2LS system in Dallas or New Jersey, said John J. Pembroke, company president. Besides providing basic property information, the M2LS can also display a color image of the home on a computer or as part of a printout, Pembroke said.

Coincidentally, a Salt Lake City-based financial consulting firm, RESources Inc., said it hopes to operate its MLS alternative this year on a nationwide basis, said Frank Weinrauch, the firm's president.

The company already has completed a series of tests over the past two years in an undisclosed market located in the intermountain region around Salt Lake City, Weinrauch said.

The RESource system uses a proprietary method of compiling the same information found in Realtor-run multiple-listing services but without relying on Realtors for the data, Weinrauch said.

The RESource database also includes properties often not found in Realtor-owned multiple-listing services, namely those for sale by owners who have not listed with a real estate agent and foreclosures owned by banks, the Department of Housing and Urban Development, and the Resolution Trust Corp., Weinrauch said.

Although the two upstart systems resemble each other in some ways, there are fundamental differences.

The American Financial Network operation closely parallels the operations of a Realtor-run MLS in that the sales agents providing the listings for the database create a contractual basis for other Realtors to earn a commission by supplying a buyer for the property.

The RESources system is designed primarily as an information service for home buyers, although realty agents may also prefer its broader listing base to the Realtor-run multiple-listing services, Weinrauch said. The firm sells two weeks of listing information in book form for $7.50, Weinrauch said, although eventually users who subscribe to computer information retrieval services can conduct a listing search for about $2, he said.

Realtor-run multiple-listing services are particularly vulnerable these days to outside challenges for several reasons, the private challengers claimed.

Realty companies in many cities, including Washington, have to join two or more multiple-listing services to cover their selling territories. Knitting together a marketplace in this way creates problems, said Stephen H. Murray, co-editor of Real Trends, a trade newsletter for real estate sales managers.

"The refusal {by adjacent MLSs} to cooperate, consolidate, cut costs and improve technology to benefit the broker and the customer ... is a great disservice to buyers {who want to see homes in an area larger than that covered by one MLS} and sellers only get homes exposed within the MLS territory."

Washington, Murray said, is a prime example of a scattershot approach. Seven different MLS systems serve the greater metropolitan area stretching from Howard and Frederick counties to the north to Charles and Prince William counties to the south.

William Ellis, Shannon & Luchs executive vice president of residential real estate, said he believes the handwriting is on the wall for the disparate collection of MLS systems here. "If the boards do not eventually {consolidate}, somebody else is liable to."

Apparently, the Realtors are beginning to take heed of such a threat. "Within our organization we are talking a lot more about the regionalization of the MLS that would allow {a single point of} access," NAR's Jaros said.

Jaros, however, dismissed the national MLS idea promoted by the private competition as "usually irrelevant" because most people move within 10 miles of home. "Real estate is not a national marketplace."

Relocation companies with real estate broker contacts throughout the country adequately serve people switching jobs in different cities, he said.

On another front, private MLS contenders can oftentimes beat Relator-sponsored listing services on price, Pembroke said. That is the case, he said, where the local boards of Realtors have subsidized board membership dues by artificially raising the MLS fee charged to list each property in the system. That works "to the detriment of large real estate brokers" who have more listings, he said.

Stephen Hicks, president of one of the larger real estate companies in El Paso, Tex., said it was just such an inequity that prompted him to begin shopping for a private MLS alternative.

Some boards, Hicks said, "charge as much as a 100 percent more than it costs to run their MLSs."

Although Murray supports the proposition that Realtor-run listing services are vulnerable to competition, he predicted that the Realtors will not give in easily.

"NAR fights hard, they fight very hard," he said. The Realtors will argue, Murray predicted, that a private MLS financed by a few large brokers is trying to monopolize the market, put people out of business and reduce customer choices.