This is to complicated and delicate question to answer on here. I strongly suggest you seek an attorney familiar with family law. Many attorneys on AVVO will give you a free consultation.
But if you want an answer in the blind I would suggest not moving in since the second you start sharing living expenses while living under the same roof will constitute a change.
I agree with Attorney Balter. If you violate the alimony decree, you are subject to the penalties within it. As Attorney Balter indicated, it is in your best interest to sit down with a specialist.
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