Timing can be everything in the real estate business, those who earn their living at it say.

One successful broker here, Dorothy Newman, has vivid memories of a sale she missed when she was first starting out in real estate.

"The Elms," the Foxhall Road home of Vice President and Mrs. Lyndon B. Johnson, came on the market suddenly when President John F. Kennedy was assassinated and the Johnsons moved to the White House. Newman felt that showing the house was a delicate matter, but she already had a client for it - Cherif Guellal, ambassador from Algeria.

She did not take him inside, but showed him floor plans and the grounds. And she wrote up a contract, which he signed.

In the meantime, an agent with another firm, less hesitand about trying to show the house, got the young ambassador inside the house. She whipped out her own contract, Guellal signed it, and the agent rushed it to those handling financial affairs for the Johnsons. The sale was consummated.

Newman, who is a widow, lost out on what would have been a $20,000 commission. She has never forgotten the incident or the lesson she learned from it.

She later branched out on her own after getting her broker's license. She has since sold property to some 30 foreign countries in the past 13 years, traveled extensively and sent two sons through college.

Perhaps her greatest coup was selling the Windsor Park Hotel to the Peoples' Republic of China for the first liaison mission here.

Newman says real estate is not an easy profession for mothers of small children - the hours are too uncertain. And she says that until the commissions start rolling in, an additional income is needed at the beginning.

Newman and other real estate professionals say they pick up valuable tips on the cocktail circuit about houses that are up for sale and who wants them.

Antoinette Hatfield, wife of Sen. Mark O. Hatfield (R-Ore.) has found the embassy circuit - where she and her husband are oftne entertained - full of tips on real estate. A controversial figure in real estate ever since she joined C. Millicent Chatel, Wise & Gilliat, Toni Hatfield went into real estate right after she bought her first investment property - through the Chatel office on Capitol Hill. She talked so knowledgeably about real estate, she was asked to take the real estate test and join the firm.

She soon mad the "Million Dollar Club," a status group of real estate agents who sell a million dollars worth of real estate in a year.

Hatfield's most impressive sale was of a $1 million Massachusetts Avenue NW property to the new Ambassador bassador of Saudi Arabia, Ali Abdullah Alireza. But an even larger sale to the Saudi Arabians fell through - and raised questions of conflict of interest involving her husband.

Mrs. Hatfied interested thed Saudi Arabians fell through - and raised questions of conflict of interest involving her husband.

Mrs. Hatfield interested the Saudis in the white marble building of the American Pharmaceutical Association next to the State Department as a chancery. The Saudis agreed to the $5 million price.

But the property's use is regulated by Congress and any review of the matter would have come before the Interior Committee, on which Sen. Hatfield serves. A spokesman for Hatfield said he would not participate in such a review to avoid a conflict.

But the proposed sale generated so much controversy on its own within the pharmaceutical organization that it was never consummated.

Like Mrs. Hatfield, some of the most successful real estate operators in the area wives of members of Congress. This infuriates John W. Gill, a Georgetown-based realtor who has 45 sales agents (the majority of them women) and a $15 million-a-year business.

Gill thought he had the inside track on the sale of the Massachusetts Avenue property to the new Ambassador of Saudi Arabia. But Mrs. Hatfield got the contract first and sewed up the deal.

He says he is opposed to all spouses of legislators in real estate. And the list seems to grow all the time.

Susan Goldaater, estranged wife of Rep. Barry Goldwater (R-Cal.), managed the Previews, Inc. office, but has recently left. Others include Jerry Wilson, whose husband, Charles, is a Democratic representative from Texas, Jolane Edwards, wife of Jack Edwards (R-Ala.); Patricia Derwinski, wife of Edward J. Derwinski, GOP representative from Illinois, and Lou Tower, whose former husband, John, is the Republican senator from Texas. Wives of former congressmen, such as Yvonne Anderson and Corinne Conte, have also been active in the business.

Gill insists these women are "unfair competition" because their husbands provide them contacts their competitors lack.

One of the most successful back realtors is Flaxie Pinkett, named Realtor of the Year by the Washington Board of Realtors. She heads one of the oldest real estate firms in the area, John R. Pinkett Inc., founded by her late father in the early 1930s. It handles several million dollars worth of real estate every year and looks after some 3,000 rental units a year.

Pinkett has set a record for community service, having been on the D.C. Board of Education and the D.C. Housing Rent Commission.

Things have changed in real estate since the days when any housewife or retired military man with time on their hands could study a couple of books, take the real estate test and get a license to sell real estate.

Eighteen years ago, when I took the Virginia sales agents test, all I studied was the Virginia Real Estate Manual and another volume, "One Thousand and One Questions About Real Estate." At the end of each chapter were a series of questions. I recall that one of the math problems in the test was taken directly form the end of a chapter in that book.

When I took the test in Richmond in 1959 along with 200 other hopefuls, the examiner told us: "Half of you will flunk. The others who pass will only eke out the barest living in real estate. Of course, two or three of you will strike it rich and make a fortune."

Well, I did pass, but I never made it big.