Possible "Sub To" deal and a question reguarding payment

[Jason Quintana]

My wifes sister currently owns a home but is struggling with the payments and will go into foreclosure at some point. She owes 89K and the house is work around 110K. Her credit is not good. If I do a sub to deal, I can get the house without a down payment, and help her out by building her credit. Her interest rate is 8% which is terrible. I would want to refinance after a year or two, is this a good Idea, and I dont fully understand how payments work. Do I write a check to her lender with my name and her mortgage number? Can I do direct withdrawl if its not my loan? Any info would help. Thanks