Currently the Haunted lot trait causes the lot to have a chance of summoning a ghost to your lot every night. The ghost itself is random so if you have multiple ghost in your game you will most likely get s different one every night. There is also a chance you may never get a ghost if no ghost exist in your game. The trait itself seems to have a pretty low summon rate and unreliable.
If the "leak" of the game details is correct the haunted house lot trait will cause the lot to have a ghost(s) that is tied to the lot/household, like roommates or butlers. They are tied to that household and can't be the roomate(s) or butler of another household unless kicked out/fired respectively.
