But by then he had been nurturing entrepreneurial ambitions. “My brothers and I were always thinking up different businesses we could start,” he once recalled, “but none of them felt right.”

A turning point came when he read the transcript of a speech by the noted economist Sumner H. Slichter, who taught at Harvard, arguing for the importance of the small business sector to the health of the postwar American economy.

Mr. Bloch soon envisioned one day starting a firm that would supply a broad menu of financial services to small businesses, including accounting, bill collection, temporary employment and tax preparation — notwithstanding the fact that he had taken only one semester of accounting in college. “I just hated it,” he said.

At 24, after a brief stint as a stockbroker and with $5,000 borrowed from a great-aunt in New York City, he and his older brother, Leon Jr., established the United Business Company in a storeroom office that they rented for $50 a month. (The great-aunt was Kate Wollman, who lived in the Waldorf-Astoria hotel and had donated the Wollman ice-skating rink in Central Park, later refurbished by Donald J. Trump, to the city.)

The brothers soon landed bookkeeping jobs for small accounts, including a hamburger stand. But growth was slow, and Leon left to return to law school.

Henry, however, held on and took out a help-wanted ad to find someone to replace his brother. It drew a response from his mother, who suggested that he team up with his younger brother, Richard, a graduate of the Wharton School at the University of Pennsylvania.