How to summon Guidry in non haunted house?

You probably need to spend a couple nights at a haunted house, waiting for Guidry to appear, and then ask him for a Paranormal Investigator license. (Note: it might take more than two nights for Guidry's first appearance.) The ability to summon him at the seance table comes from the license I think. Alternatively, you can buy the license from the Rewards Store for 3000 satisfaction points.