Marion (Duke) Greene has been working since he was 8, cleaning nightclubs, selling newspapers, tending bar, waiting tables and selling flowers, among other things.

"I worked seven days a week, but I didn't know any better," Greene remarked earlier this week as he discussed the sale of International Business Services Inc., the multimillion-dollar computer-services business founded 16 years ago in the basement of his Washington home with only $500. He nurtured the fledgling management- and technical-consulting company to an enterprise with estimated annual sales of $28 million, making it one of the largest minority-owned businesses in the country.

He recently sold IBS for $6 million to a California high-technology company as a way to ensure continued growth after it got too large to participate in the Small Business Administration's minority-business assistance program.

Greene will continue as president of IBS, however, and operate it as a major subsidiary of Comarco Inc. of Anaheim.

Greene, 48, built IBS with an investment of personal savings and long hours that turned into years without time off.

In the early years, Greene took part-time jobs at night to help pay the company's expenses. "When I was running short on capital, I drove trucks at night," he said.

IBS was not Greene's first experience as an entrepreneur.

"I got through college cutting hair," he recalled.

Greene did a good deal more than cut hair to help earn a degree in mathematics from Morehouse College in Atlanta. During the summer, while working as a waiter in Atlantic City, N.J., he used the same skills that helped build IBS to develop a thriving diversified student-run enterprise.

"I collected soap pieces and made them into the shapes of roses and lemons and sold them," Greene recalled as he described an ingenious enterprise that he built, collecting used soap from guest rooms in the hotel where he worked.

From a mixture of soap that he boiled, Greene recolored and added perfume to batches that he reshaped in molds patterned after fruit and flowers.

To supplement his income from a waiter's job and the brisk trade from soap sales, Greene collected newspapers and sold them to a recycling company.

Greene eventually enrolled in dental school but was forced to drop out -- because the demanding class and study schedules prevented him from working to earn enough to pay for his education.

He later went to work as a programmer in the Defense Department. Still driven by the entrepreneurial spirit, he formed his own management- and technical-consulting firm -- which became IBS.

Glenn Buell, Comarco's chairman and chief executive officer, described IBS' management as "superb," and said that it would remain intact with Greene as head of the new subsidiary. A primary goal for the new acquisition, Buell added, was to "focus [IBS] more on profitability and provide [it] with the strength [needed] for competitive procurements."

Greene said his decision to sell IBS stemmed from the need for "additional corporate resources and access to capital."

Although it is considered one of the country's more successful small businesses, like most small-business enterprises, IBS' growth has been tempered by its lack of the capital required to compete against larger companies. IBS was forced to graduate from the Small Business Administration's 8A set-aside program for minority contractors when it became too large to be considered a small business. And competing against bigger companies without a stronger capital base would have been difficult, according to Greene.

"When you graduate from the 8A program , you either die or you try to find a compatible company," Greene said, explaining his decision to sell IBS.

Buell said he became familiar with IBS' operations when the two companies worked on the same defense contracts for the Army. He said he subsequently developed an interest in acquiring the Washington firm to complement Comarco's operations.

Comarco, which has a division in Arlington, is an engineering and product-services company. About 80 percent of its work is defense related.

"Comarco specializes in hardware, and we have a tremendous capability in software that we developed over 16 years," said Greene, who added that he wasn't planning to sell IBS when he was approached by Comarco officials.

IBS has a staff of more than 600 full-time employes, providing a wide range of computer and related training services, primarily to U.S. government agencies. In addition to its headquarters on Vermont Avenue NW, IBS has offices in Manassas, San Diego, Denver, Miami and Cairo.

Black Enterprise Magazine last year ranked IBS as the 73rd-largest black-owned firm in America, based on sales, and identified it as one of only seven high-technology companies on the annual BE Top 100 list. Also last year, IBS was named "small business of the year" by the Washington district office of the SBA.

A diversified company that specializes in a broad range of services, IBS has completed more than 400 projects under contract to government and industry clients. Its operations include the management of parking facilities at National and Washington Dulles International airports.

Two years ago, IBS was chosen by the U.S. Agency for International Development to develop and implement an automated social insurance system for the Egyptian government.

Comarco reported sales of approximately $40 million in 1985, and revenue is expected to double in 1986, according to Buell. Comarco's stock is publicly traded on the over-the-counter market.