Complex sentence: To make ends meet, Leavitt wrote a number of corporate histories, including that of the Pennsylvania Salt Manufacturing Company, and wrote for publications of the Great Northern Railway Company; he also continued to dabble in advertising and public relations.
Split into simpler sentences: To make ends meet, Leavitt wrote a number of corporate histories, including that of the Pennsylvania Salt Manufacturing Company, and wrote for publications of the Great Northern Railway Company. Leavitt also continued to dabble in advertising and public relations.