Once your Sim finishes searching for ghosts, they'll stand still with a red icon over there head. You have to get to level 6 before making all the ghosts available, let alone actually finding them, but you should find 10/12 before even getting to level 6. Choose one Sim (no real point in doing multiples here) to search for ghosts over and over and over.
That house comes with a free Skeleton, which is one of the best haunted items you can get.
The Life of Excess achievement in The Sims FreePlay (WP) worth 30 points Buy the Pro Skater’s Dream Pad.
