After graduating, Freeman started his career at the Essex water power company as assistant to the company's engineer, Hiram F. Mills. In those days he became acquainted with other leading engineers such as Charles Storer Storrow, James B. Francis, Joseph R. Davis and John C. Hoadley. In 1886, he moved to Boston, where he was appointed engineer and inspector at the Associated Mutual Fire Insurance Company. In the next decades Freeman was the design engineer for several water projects, served on several water works commissions, and was consulting engineer for many projects.