He owned a shipyard.

Walk west to the Rodman House, located at 520 West Main. This dwelling, constructed in 1848, was once the home of two justices of the North Carolina Supreme Court. Before the house was constructed, a shipyard at the site was opened and operated by Hull Anderson, a free black who later emigrated to Liberia.  Because much of Washington was burned during the Civil War, the Rodman House is one of the few surviving antebellum structures in the town’s historic district.

From Daniel W. Barefoot, Touring the Backroads of North Carolina’s Upper Coast (1995).

See also, http://www.wdnweb.com/2013/02/21/pamlico-rivers-past-hull-anderson-black-shipbuilder-in-1800s-washington/