When Ruby Mignott could not get a loan to buy a home in 1979, she invested $10,000 in a down payment on a Rockville lot after friends and realty agents advised her to buy property. By owning land and making monthly payments, Mignott would demonstrate that she could meet her financial responsibilities and probably would qualify for a loan within a year, the advisers said.

In 1980, after a year of making the $96.50 monthly payments on time, Mignott returned to the banks and savings and loan institutions. Again she was turned down. Build part of the home with your own money, then reapply, the institutions told her.

With $20,000 in cash invested and a half-finished basement on the Rockville lot, Mignott has spent the past several months seeking financing for the home she has dreamed of building since she arrived from Jamaica in 1969. She has written nearly every politician in the county, including Democratic Rep. Michael Barnes and County Executive Charles W. Gilchrist, who she said tried to help her. She has contacted county and private housing agencies. She has applied for low-interest, first-time homeowners' loans and low-interest construction loans from the county.

Each time she has been rebuffed. Banks and savings and loans now tell her there is no money available and will not take her application. Politicians put her in touch with agencies that put her in touch with other agencies that eventually tell her there is not much that can be done, Mignott says. When she applied for one county loan, she was told she needed letters from two banks verifying that she had been turned down for a loan. One bank agreed to write the letter--for a fee of $125.

"I've worked so hard to do this. I wanted to prove to my children that a single woman can help herself. I wanted to be a model for them. But it just doesn't work," says the 41-year-old Mignott, a case worker in the Montgomery County Social Services Department, who became an American citizen two years ago.

Over the past decade, higher-paying jobs, greater social independence and less discriminatory credit rules all have made it easier for women to buy homes, and more and more have become homeowners.

Despite these gains, however, Mignott, who earns $14,800 a year, and millions of women like her in middle-income jobs find the housing market as tough to penetrate today as it was a decade ago.

"It (the housing market for women) is like four blind people looking at different sides of an elephant. Each problem is different," explained Arlene Simons, director of the Montgomery County Community Housing Resources Board, who participated in a Montgomery workshop Saturday to aid women in locating housing.

"First, on one side you have the horrible economics of our time. Second, you have the number of single women heading households increasing daily, with a number of these women entering the housing marketplace for the first time. Third, women are being paid less than men and fourth, we have institutions still dealing with subliminal, institutionalized discrimination against women."

Despite federal housing laws prohibiting discrimination based on sex, Simons says, many women unwittingly are the victims of landlords and financial institutions that don't feel women are as financially stable as men or do not want single women renting in their building. A 1977 study by the Department of Housing and Urban Development showed that women had a higher chance of having their applications denied or their property valued at a lower rate than men when determining eligibility for loans.

Most human rights officials also agree that the number of sex discrimination cases in housing filed by women is much lower than the actual number of incidents. The majority of housing complaints filed by women are based on race, not sex, according to Montgomery County Human Rights Commission official Michael Dennis.

"It's only logical, really, that if a black woman or a Hispanic woman is denied a house, the easiest thing to do is file a race discrimination suit," Dennis said.

In Montgomery County, of the 28 housing discrimination cases filed last year, four were filed on the basis of sex. In one instance, a man who owned a home with a yard didn't want to rent to a woman because he felt the woman "needed a good strong man to take care of the big yard around the house," Dennis said.

Nationwide, 336 housing sex discrimination suits were filed last year, according to HUD figures.

The number of women who own their own homes has increased 60 percent during the past decade--from 6,452,000 to 10,289,000 nationwide, according to the U. S. Census Bureau's 1980 Annual Housing Survey. But the difference between 1970 and 1980 for Mignott and many others is that they have more family members to support and less money, and face a housing market beyond their reach.

Interest rates and housing prices have skyrocketed. Recently released census figures show that the average price of a home in Montgomery and Prince George's counties increased almost 300 percent from 1970 to 1980--from $32,700 to $97,400 in Montgomery and from $23,700 to $64,500 in Prince George's. More women were heading households in 1980 than in 1970, with the number in Montgomery rising from 10,508 to 18,591 and in Prince Georges' from 15,926 to 30,259.

And women's salaries are 40 percent lower, on the average, than that of men, according to a National Academy of Sciences report.

In addition, Simons said, many women who want to rent in Prince George's and Montgomery, particularly women with children, are being squeezed out of the market by the same factors facing those who want to buy.

According to census figures, the average apartment in Montgomery County rents for $332. If a woman followed the traditional rule of not spending more than a quarter of her income for housing, she would have to earn almost $16,000 to afford the average apartment. In Prince George's the average rent is $282.

Nationwide the situation is equally grim. Only 53 percent of all female-headed households pay a quarter of their income or less for rent, according to a 1978 Housing and Urban Development study. The problem grows worse as women grow older, with more than 75 percent of those over 65 paying more than a quarter of their income for rent.

"Women have a systematic disadvantage in the housing market," says Judith Vaughan Prather, head of the Montgomery County Commission for Women. "Women make less money than men."

Maryland women face another major hurdle in the rental market: It is legal in the state to bar families with children from rental apartments. In Montgomery's Bethesda-Chevy Chase area, 2,805 of the 7,714 rental units available prohibit children, according to the most recent apartment directory prepared by the county.

The District of Columbia, plus nine states and several cities and counties around the nation, have enacted legislation prohibiting landlords from discriminating against families with children. A recent California state supreme court ruling that children cannot be barred from rental housing could prove to be a landmark case if the U.S. Supreme Court agrees to hear an expected appeal by California landlords.

"The whole feminization of poverty is enormous and Montgomery County is not immune," says Simons. "For the most part, women are not sophisticated about the housing market and as the poverty level for women creeps up it has to get worse."

To help lessen the problems, a number of Maryland groups have begun to look for ways to help women find housing they can afford. Umbrella groups in Prince George's and Montgomery offered women's housing workshops this month.

Operation Match, a Montgomery-based group with branches in Prince George's and other jurisdictions in the Washington area, matches up renters with people who have rooms to rent. Although Operation Match is open to men, the majority of its clients are women, with 70 percent being single heads of households and half earning between $9,000 and $13,000. A Woman's Place, an arm of the women's commission, has begun to educate women on how to find housing. In 1981 the agency received 190 calls from women seeking advice on housing problems, according to Vaughan Prather.

For Mignott, the frustration of being a moderately paid woman trying to build a house in the 1980s is at times overwhelming.

"I have tried everything. You can't believe how I have lived to save money to build my own house," says Mignott, a woman with a lovely heart-shaped face and melodic voice. She was interviewed in her three-bedroom apartment in Rockville, where she lives with her two children. The former head of voter registration in Jamaica, Mignott said she fled Jamaica because she feared political repression. She will receive her bachelor's degree this summer from the University of Maryland after going to night school since 1974.

"I love America, I love being an American citizen. I feel I have a debt to America--that is why I am a social worker," she said. "But the America that promised so much--the America we talked about--is wrong.

"The big fish don't want to listen to a woman like me."