What religion are you? (Not a question really)
You could tip a priest to come and bless the house. My mother has it done every year. She pays him about $20. He walks through the house saying prayers and sprinkles holy water around. He'll also bless and sprinkle anyone who stands still long enough.
This is an Orthodox Christian priest. I don't know if Catholics or other denominations do it. Do you know any Greeks, Serbians or Russians? If approached appropriately and for a small donation they should come to your house regardless of your own beliefs. Tell him about the ghost and he'll say "the prayer for the dead".
What have you got to loose? The twenty bucks would cover his fuel costs only.