His executive offices in Mexico City are spartan. He dresses unpretentiously in baggy suits, sometimes drives his own car, lives in the same house where he raised his six children and has been seen wearing a cheap plastic watch. But don't be fooled by Carlos Slim Helu's austere life-style; appearances notwithstanding, Slim is the richest man in Mexico, and he is a new player in the rapidly evolving digital dimension.

Two weeks ago, Slim, 56, and his Grupo Carso conglomerate joined with International Wireless of Cambridge, Massachusetts, to buy Prodigy, the floundering online computer service owned by IBM and Sears. Grupo Carso owns 20% of International Wireless, which paid an estimated $250 million for Prodigy. "This is an outrageously great opportunity," exults I.W. chairman Gregory Carr. "We're going to take Prodigy to the world."

If Slim's record as a shrewd bargain hunter is any guide, Prodigy, which ranks fourth among American online services, may indeed become a hot property after years of losing money. Over the past decade, this Mexican-born son of Lebanese immigrants has earned a reputation as a turnaround magician--snapping up undervalued, badly managed companies, then putting in new executive teams to bring them back to profit. Slim's vast holdings, valued at around $3.4 billion, encompass everything from tobacco farms to copper mines to printing plants. Slim owns Mexico's beloved Sanborn Hermanos chain of coffee shops and drugstores, the Inbursa financial group, plus a big interest in the Mexican phone company, Telmex, of which he is chairman.

When Mexico's economy was flying high in the early '90s, Grupo Carso was capitalized at more than $10 billion. Since the disastrous December 1994 devaluation of the peso, that value has dropped sharply. But because of Grupo Carso's relatively small debt and heavy reliance on exports, amounting to as much as 40% of its business, the company has suffered little. Profits for 1995 were $295 million. "Carso is no upstart," says Santiago Pique, an analyst at Bear, Stearns in New York City. "The company is a Mexican success story."

The purchase of Prodigy is part of a strategy that may ultimately make Grupo Carso a power in the communications revolution. All the company's telecommunications properties, including Telmex and International Wireless, are being split off into a new entity called Carso Global Telecom. Prodigy has been outperformed by competitors in the U.S., but Carr says he will take Prodigy "immediately" to Mexico through the Telmex phone network, and then to all the rest of Latin America. Work will begin soon on providing Spanish and Portuguese content. International Wireless also owns Internet properties in Asia and Africa and is thus well positioned, says Carr, to exploit the global market.

Given Prodigy's potential, Slim and his partners bought the service for peanuts. Jamie Kiggen, an Internet analyst for Bear, Stearns, believes that $150 million of the $250 million price was in debt assumption, which means International Wireless put up only $100 million in cash for a company in which IBM and Sears had invested $1 billion. Alfredo Sanchez, director of Carso Global Telecom, emphasizes that his company will tread carefully on this new turf. "Our strategy is to go slow," he says, "to first learn about the market through smaller investments. We want to be cautious."

That kind of prudence has always been Carlos Slim's hallmark, learned from his immigrant father, who started amassing a tidy fortune in real estate during the Mexican revolution. He made his first investment--in a government savings bond--at age 11. By the time he graduated from college with an engineering degree, he had accumulated enough wealth to invest in a bottling plant, a stock brokerage and other businesses. These later became Grupo Carso--derived from his name, Carlos, and that of his wife Soumaya Gemayel, who is a member of one of Lebanon's most important Maronite Christian families. Slim joined the billionaire club during the Latin American debt crisis of the early '80s, when, because he was flush with cash, he was able to buy a long list of struggling companies for as little as 5% of their worth. Within 10 years the market value of the companies had increased 3,000%--in part because of his slash-and-burn tactics for cutting costs and payrolls. His detractors say some of the purchases were greased by his close ties to the ruling Institutional Revolutionary Party.

Slim chose not to go on a similar buying spree after the more recent peso crash. But he has quietly expanded Grupo Carso's stake in Telmex, which at one point lost half its stock-market value, from the original 5% to 8.5% today. He also scooped up two other communications companies for $45 million before joining the group that bought Prodigy. Can the new management make Prodigy prosper? No one who knows Carlos Slim's ability to take a company from distress to success would bet against it.

--Reported by Laura Lopez/Mexico City