How to legally pay for a mortgage on house I don't own?

Here is the situation. I live in Phoenix Arizona and lived with my mother while in college. After college I started to work from home on small business and it is going well. My mother is moving out to live with her boyfriend and I am staying in the house. I will be paying her the mortgage and I will be paying all the associated bills. Her name is on the mortgage, as no bank will give me loan yet to put it in my name.

I would like to claim the mortgage I am paying as tax deduction for next year, but since I do not own the house I do not believe that I can state on taxes that I do and deduct the mortgage from it, as my name is not on it. I am technically renting. If we make a formal renting agreement I can then claim the rent (mortgage) on taxes, but then she will have to claim it as income on hers, so the tax is transferred from me to her; no win there.

Is there a way for me to pay the mortgage where she does not have to claim it as income and where I can deducted it from my taxes, legally? Refinancing and putting my name on mortgage is not an option at this time.

Thanks

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