I was doing a little reading up on the late actor and in an interview in 1979, said he had co ownership of The Odd Couple! What that exactly means, I am not 100% sure. I do know that Garry Marshall bought the rights from Neil Simon. I wonder if he owned the rights with Marshall or maybe even Jack Klugman.

He, and probably Klugman likely own/owned a small piece of the show and therefore receive a chunk of any profits from it. A fairly standard thing for a major star of a show like that. Another example: Dick Van Dyke is one of four owners of "The Dick Van Dyke Show." (The others were Danny Thomas, Sheldon Leonard, and Carl Reiner.)