Don't assume you have a demon and call an exorcist. In my entire life I have yet to encounter anything even remotely demonic. Most ghosts will leave quietly when asked to . I personally don't charge for a house visit. But I know legitimate people who do, mostly because they are so much in demand and a fee weeds out the curiosity-seekers.
Travel expense are also a legitimate request.
Just watch out for ghostbusters who want lots of cash. Or you could just enjoy your ghost. I know many people who say that their ghost is company for them, or it does helpful things. Most ghosts are just lost people, not hostile or violent spirits. If you were a good person before you died, you'll probably be a pretty mild-mannered ghost.