Frederic Massena wants to write a book on the sociology of his native Haiti some day. In the meantime, he is making about $60 a week fixing appliances and sleeping in his boss's little shop to save on rent.

Directly across Second Avenue in Miami's Little Haiti, Viter Juste has added a lunch counter to his Haitian bookstore. The Immigration and Naturalization Service is moving its local headquarters into the neighborhood, he explains, "and that will create a lot of new traffic for me."

The two Haitian immigrants have little in common, but illustrate the economic scrambling and self-reliance that seem to characterize the thousands of Haitians who have washed up on Florida's shores to escape the poverty and repression of their Caribbean island, just as it characterized many European immigrants a century ago.

The Haitians' determination to get ahead, combined with restrictions on welfare eligibility and concern for their immigration status, in only a few years have propelled them ahead of their neighbors in Miami's black American ghettos, according to several economic and social measuring rods.

As a result, resentment has arisen among some young American blacks who call Haitians "Uncle Toms" and accuse them of undermining the job market by accepting misery wages.

"There have been no explosions, but there is a lot of resentment," said the Rev. Ray Fauntroy, who has helped organize the city's poorest black area, Overtown, which gained notoriety last December when it was shaken by street violence.

The difference in the two communities has been easy to see for some time. The streets of Overtown show bleak, sagging apartment buildings, a few bars and mom-and-pop stores, and a lot of boarded windows.

Beginning about 15 blocks to the north, Little Haiti shows similarly dilapidated housing. But it also leaves an impression of vitality created by bustling sidewalks and more than 100 small restaurants and enterprises ranging from "La Femme Elegante," a dress shop, through "Au Beurre Chaud," a bakery, to "Aux Palmistes," a restaurant serving Haitian specialties.

A recent study by the Behavioral Science Research Institute of Coral Gables, Fla., has allowed Miami and Dade County officials to look beyond the appearances. What they are finding, among other things, is that the 22,000 immigrants in Little Haiti are hustling to make a living and send money home despite language, education and culture barriers that contribute to an unemployment rate of nearly 50 percent.

Ninety percent of Haitian youths aged 16 to 19 are enrolled in school, compared with 70 percent for Dade County as a whole and a still lower, but unrecorded, proportion for Overtown. Nearly a third of Haitian adults also are enrolled, many in language classes or job training.

"Under a real language obstacle, they seem to be sticking in there, whereas some of our American blacks get discouraged and drop out," said Joe Sharon, who handles placement and followup for Dade County schools and training centers.

Twenty-eight percent of Little Haiti's residents receive food stamps, the study showed, and 13 percent get other forms of government aid. Florida state officials estimated that 35 percent of households in the area encompassing Overtown receive food stamps, with Overtown's own unknown rate likely to be higher.

However, the Rev. Gerard Jean-Juste, who heads the Haitian Refugee Center, said much of the difference between Overtown and Little Haiti is due to restrictions that prevent recently arrived Haitians from receiving U.S. government aid such as welfare or food stamps.

"Sometimes we don't even know about them," he added. "In Haiti we don't have them. But there are many who are entitled to go on welfare but who refuse out of pride. They also are afraid that if they go on welfare, they will not get their residence status."

Status with U.S. immigration authorities is a major concern in Little Haiti. When the Carter administration granted provisional immigration rights in 1980 to Haitians and Cubans, nearly 20,000 Haitians were processed by the Immigration and Naturalization Service and given a "status pending" permit to stay.

INS officials estimate that only 40 percent of those who arrived in 1980 have registered, meaning the actual count in Little Haiti and elsewhere is sharply higher than many official statistics have shown. In any case, the firm that did the recent survey said Little Haiti's 22,000 residents make it the largest single concentration of Haitians in the United States.

Jean-Juste said one reason for the Haitians' economic performance here is that those who make it to Miami are often the most energetic and able from their home villages. Sometimes they are sent off after a collection of money from family and friends. Others have enough to pay their own way, he added, challenging the idea that Haitian immigrants were all desperately poor back home.

"It is the contrary," he said. "The poor ones are back in Haiti. They can't make it."

Massena, for example, said he attended the same secondary school as President-for-life Jean-Claude Duvalier and Michele Bennet, the daughter of a wealthy merchant who has become Duvalier's wife.

Fauntroy, whose brother Walter is the District of Columbia's delegate in Congress, said the difference also reflects racism and economic discrimination that prompt the most able Overtown blacks to move on for better opportunities, leaving behind the poor and less motivated.

"They Haitians are not depending on the government, as the government has forced poor folks to do in the United States," he added. "They Overtown blacks have been beaten down by the Jefferson Davis mentality to the point where they have submitted to the will of those in control. They have given up."

Ray Goode, a developer and former Dade County manager who has invested in Overtown renewal projects, said Haitian immigrants also have displayed a willingness to stick together that makes their neighborhoods more prosperous than Overtown and other nearby areas.

In addition, he said, Overtown's crime rate discourages small businessmen from taking a chance. Overtown, with a population of about 4,500, recorded slightly more than 2,000 major crimes in 1982, according to Miami police files. Little Haiti, with five times the population, recorded about 3,000, the files show.

Loretta S. Titterud, who managed the recent study, said interviews indicated Haitian immigrants move into more affluent areas when they can afford it, leaving their less successful countrymen behind. The result after a generation or two, she warned, could give Little Haiti some of the same problems facing Overtown if nothing is done to prevent it.