Equity in Mother's home

[Nicholas Reece]

Hello and thanks for any assistance.  Years ago I moved into my mother's house and began renting, as she moved out of state.  As roommate challenges and repairs began to stack, we worked out an agreement for a rent to own solution.  We have since paid off the mortgage.  The house is owned free and clear by my mother.  I did a remodel on it, bought another home, and now rent it out.  We have agreed that I am to pay her roughly $45k, in $500 monthly payments until paid off. 

My intentions are to pay her off immediately, and use my current "equity/ownership" in the home to reinvest.  I estimate the house to value at $120k or more, currently.  Ideas?  Legal/Tax hurdles?  

Thanks again!!