Well, I understand that point. Therefore, all advertisements must be carefully worded. Without a doubt, they can't guarantee that anything will happen. However, if they're advertising the ability to explore historic sites, while offering tours and such it is a different story. In those cases, they are offering a service.
For example, Rolling Hills Asylum. Rolling Hills charges strictly for admission to search for paranormal activity. This could be seen as a liability, as they offer no other service. They do offer tours, yet an additional fee is expected.
Therefore, places that include a package deal including a tour / historic walk through appear more credible, and can arguably offer a service worth monetary value.
Moving on, I hope the comment "If your in it to make money perhaps the paranormal is not an area for you", wasn't directed towards me. My team investigates completely free of charge, as we feel it is inappropriate to do otherwise.
No, money shouldn't be an incentive in this field. However, money shouldn't be an incentive in too many things that already are. Healthcare, for example.
What can you do? Just don't go then.