Primary Residence Benefits

[Andrew Ware]

Due to my mother's medical condition we are living basically rent free at my parents house.  Unless/until we build a house on the same property or something changes it is unlikely that we will move out.  So my primary residence is basically being wasted.  

Are there any creative ways that I could use this designation on another property for loan and/or tax purposes?  I'm assuming it truly means that I need to live in the house.  What if I put an office and bed in half of a duplex?  I want to steer well clear of trouble, but I wouldn't mind "changing my mind" post rehab and not moving in after all.