My mother passed away in 2016. I inherited her primary home. It has mortgages on the property that I was a co-signer for. I am making payments. How do I handle this?

I was a co-signer but not on the deed.  It is my property now.  I am making payments, paying utilities, doing repairs, paying insurance an taxes, etc.  How do I file this property?  What can I claim?  How do I determine basis?  What if I rent or sell?  Can I claim mortgage interest even though she was the primary on the note?  Thanks