Answer by taking a quote from the following article:

Kasem was born in Detroit, Michigan, on April 27, 1932, to Lebanese Druze immigrant parents, who had settled in Michigan, where they worked as grocers. Kasem was named after Turkish leader Mustafa Kemal Ataturk, a man Kasem said his father respected. In the 1940s, "Make Believe Ballroom" reportedly inspired Kasem to follow a career in radio and later host a national radio hits countdown show. Kasem received his first experience in radio covering sports at Northwestern High School in Detroit.

After the war, Kasem began his professional broadcasting career in Flint, Michigan. From there, he spent time in Detroit as a disc jockey for radio station WJBK-AM (and doing such shows as The Lone Ranger and Sergeant Preston of the Yukon); WYSL in Buffalo, New York; and a station in Cleveland before moving to California. At KYA in San Francisco, the general manager first suggested he tone down his 'platter patter' and talk about the records instead. Kasem demurred at first, because it was not what was normally expected in the industry. At KEWB in Oakland, California, Kasem was both the music director and on-air personality. He created a show which mixed in biographical tidbits about the artists' records he played, and attracted the attention of Bill Gavin who tried to recruit him as a partner. After Kasem joined KRLA in Los Angeles in 1963, his career really started to blossom and he championed the R&B music of East L.A.  Kasem earned roles in a number of low-budget movies and acted on radio dramas. While hosting "dance hops" on local television, he attracted the attention of Dick Clark who as a producer hired him to co-host a daily teenage music show called Shebang starting in 1964. Kasem appeared in network TV series including Hawaii Five-O and Ironside. In 1967, Kasem appeared on The Dating Game, and played the role of "Mouth" in the motorcycle gang film The Glory Stompers. In 1969, he played the role of "Knife" in the "surfers vs. bikers" film Wild Wheels, and had a small role in another biker movie, The Cycle Savages, starring Bruce Dern and Melody Patterson.  Kasem's voice was, however, always the key to his career. At the end of the 1960s, he began working as a voice actor. In 1969, he started one of his most famous roles, the voice of Shaggy on Scooby-Doo, Where Are You! He also voiced the drummer Groove from The Cattanooga Cats that year. In 1964, Kasem had a minor hit single called "Letter From Elaina". A spoken-word recording, it told the story of a girl who met George Harrison after a San Francisco concert.

what did casey do in early career?
he spent time in Detroit as a disc jockey for radio station WJBK-AM (and doing such shows as The Lone Ranger and Sergeant Preston of the Yukon);