General Questions-Domestic Partnership, Home Business

My sig. other started a new job. We filed for a domestic partnership this month as well. I am a stay at home mom. He is claiming me as his dependent. The house is in my name. Can he claim the interest on the mortgage since I am his dependent? Also, I am starting a home business. Can he deduct home business start up costs if I do not make any profit from the business yet this year?
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