During World War II, Kelley served as an enlisted man in the United States Army Air Forces from March 10, 1943 to January 28, 1946, assigned to the First Motion Picture Unit. After an extended stay in Long Beach, California, Kelley decided to pursue an acting career and relocate to Southern California permanently, living for a time with his uncle Casey. He worked as an usher in a local theater to earn enough money for the move. Kelley's mother encouraged her son in his new career goal, but his father disliked the idea. While in California, Kelley was spotted by a Paramount Pictures scout while doing a United States Navy training film.