This button requires both the 
    Advanced setting and the Selected Household must also be different than the 
    one where the selected character currently resides. For moving characters 
    from household to household and for most NPC and Townie type characters the 
    move in button can be used without any problems. Some of the NPC characters 
    may cause game play issues though if they are moved in a household. In 
    particular it seems that the Headmaster does not do well when moving into 
    the household and under some circumstances even disables the build and buy 
    buttons for the game. I would suspect that the social worker may also cause 
    problems since people who have never used this program or modified the game 
    in any way have had some problems caused with the social worker when they 
    visited. (I've seen this first hand myself)
    Before moving characters into the household it 
    is a good idea to have a change of clothes ready for them beforehand and you 
    should have them go to a mirror and use the "Change Appearance" option right 
    after they arrive. It isn't necessary to actually make any changes but you 
    will need to save. This will be especially important if they show up without 
    a face. Otherwise they will walk around with a big hole in their head. If 
    you move an NPC into a household with this then the game will generate a new 
    NPC to take over their job and they will need to find a new job.