Am I eligible to take mortgage deduction

I wouldn't think so. The whole point of a mortgage deduction is to offset income.

No, because the 1098 (that shows mortgage interest paid) will be issued by the bank in your mother's name and social security number. Get her to take the deductions.

No. As described, you are neither the shareholder or the mortgage holder. You are only a tenant, with no ability to deduct or offset interest or taxes.

Everyone above is correct based on my experience. If you take the deduction, it will result in an IRS inquiry because your name doesn't match the 1098 issued by the bank at year's end listing the mortgage interest. My own experience with this resulted from my then boyfriend and I taking out a mortage together. The mortgage listed us both as mortgagors, but the 1098 form only had room for one of our names so his name appeared. Each year we we split the deduction according to the percentage of the mortgage we each paid, the IRS sent me a letter demanding I pay a penalty and back taxes or that I submit proof of eligibility for the deduction (meaning a copy of the loan agreement). Each year my accountant would take care of providing the proof and the matter would be resolved. But it was annoying. When we refinanced we made sure the bank would list us both on the 1098 and it hasn't been a problem since then. Lesson: the IRS pays close attention to this stuff.

A belated thank you to all who answered.