Timberlake began his working career between 1916 and 1920 as a railroad agent for the Canadian National Railway. His succeeding jobs were passenger agent, Union Pacific Railway, 1920–22; accountant, Bingham and Garfield Railway, 1922–23; accountant, Union Pacific, 1923; chief clerk, Nevada Northern Railway, 1923–27; general auditor, Illinois Terminal Railway system, 1927–32. He next went into the travel industry, with a half interest in the Southern California Tourist Bureau, after 1932. Later he was full owner of the agency, which became the largest independent travel bureau in California. He also worked at times for the Kennecott Copper Company and Illinois Power and Light.