Daniel K. Ludwig, a reclusive billionaire once considered the world's richest man with a fortune estimated at $3 billion, died in New York yesterday at age 95. Son of a real estate agent in South Haven, Mich., he left school at 19 and borrowed $5,000 to buy a steamship to carry molasses on the Great Lakes. In 1921 he bought his first ocean-going vessel and by 1930 had switched to carrying oil. His worldwide businesses eventually included not only a fleet of merchant ships but oil wells, refineries and substantial property holdings. In his later years he tried to carve a commercial empire out of Brazil's Amazon jungle, but the $1 billion project turned sour and he sold it in 1982. In a rare interview, the ruthless negotiator once told Fortune magazine: "For a couple of years I was barely one jump ahead of the creditors. In fact I was broke all the time, but I didn't know enough to lie down."