From what I read he got onto Miami radio in 1957 so chances are he left UPS when he got on the radio. His dream was to either be on TV or on radio. He worked for UPS when he thought that would never really happen.
Despite dreams of a radio career, King became distracted by the tragedy in his family and thus found it hard to concentrate in high school. Rather than pursue higher education, King worked several jobs in order to help his mother out, one of which included a UPS deliveryman. While in his 20's, King would pay visits to radio stations in New York, and on one occasion, met with a CBS staff member who suggested that King go to Florida to pursue a radio career.