If the celebrity is a real celebrity, not somebody who had a role in Love Boat 30 years ago, that would be worth considertation. You will not get film actors/actresses.  Be preapred for televison or sports celebrities. The celebrity should be perceived as "current" and "relevant" not a has-been. Dont overpay for celebrities.  You can usually get them for a decent one day shooting fee plus a point off the back end.  I would personally use a celebrity as a co-host, allowing the other co-host to carry the "selling" in the show.