Historic locations that do promote the haunted nature of their location, and then charge money for tours, investigations, and other forms of access to their site aren't doing anything wrong. it is incredibly difficult to maintain an historic site. It can be hard to find a method for raising money to support the staff, maintenance, and other costs associated with such a location. If a site has a legendary status as a haunted location, and there are people willing to tour it or investigate it, then it is only fair that those people help financially support the location.
The only real concern, is how honestly the paranormal nature of the location is portrayed or explained in order to market access to the location. If marketing becomes full of lies and half-truths, this is damaging to the Truth of the location.