Complex sentence: Barnes began his career in journalism working as a reporter for "The Lowell Sun" in Lowell, Massachusetts before becoming a Washington, D.C. correspondent for "Newsweek" and was subsequently employed as a west coast correspondent for "The New Republic".
Split into simpler sentences: Barnes began his career in journalism working as a reporter for "The Lowell Sun" in Lowell, Massachusetts. He later became a Washington, D.C. correspondent for "Newsweek" and was subsequently employed as a west coast correspondent for "The New Republic".