Help Set up deal for my sisters house

My sister needs to move now for work and is asking me to buy her house. I’m not sure how to set the deal up. She has a loan at 4% interest and owes $75k she has been paying for 10 years. She bought house for $150k and wants $190k. It’s probably worth about $210k. She is willing to take a 10% down payment and have me take over paying the loan. But not sure where to go from there. Help appreciated.