In 1851, he was appointed agent to the Mutual Life Assurance Company of New York and the Western Assurance Company of Toronto, Ontario. By the early 1860s he was the secretary-treasurer of the Montreal Permanent Building Society, which became the Montreal Loan and Mortgage Company in 1875. He was named its president a couple of years later, a position he held until his death. Many of the investors in the syndicate which controlled the society were to remain associated with Gault in other enterprises; they comprised a cross-section of Montreal merchants, bankers, and industrialists.