You need to let someone starve and then the Grim Reaper will come.

You have to make sure it happens in a room and they died of hunger.

When the ghost is in a different room delete the door that the Sim was in.

Then the Grim Reaper will not be able to get out and when he is not floating anymore buy another door.

Then when the Grim Reaper pulls out a book make your Sim talk to him so he can put it down.

Then go to build/buy mode and sell it. Jut keep on doing this till he leaves.