A mortgage needs a running account. Running account is the information provided by the purchaser, which is used to verify whether the monthly income of the purchaser can repay the loan in time. As long as your sister can repay the loan in time every month, there is no problem. But if she doesn't pay back for various unexpected reasons, the money in your running account will be deducted. If there is no money deduction, you and your sister will bear legal responsibility. Providing information with someone else's running account is fraud, but it does not harm others' interests. I'm sure your sister won't lie to you, because there is still a house to do legal work. If your sister has a problem, you can buy a house in full.