Did you know that you can formally evict ghosts in several US states. If they are tenants and they aren't paying rent you can serve them by posting the notice on the door of the haunted location. Then you can (for a fee) get the Sheriff to come out and evict the unclean spirit in compelled by the power of the Commonwealth of Virginia (or whatever state still allows you to do that).

I've never had the need to evict a ghost, but I'd love to see it.