Buying a flat on my mother's name can sister ask for her share in it

Hi! I am buying a resale flat on bank loan. I am planning to include my mother as one of the co- borrowers in loan and in deed, in order to avail off the benefit of lower stamp duty and interest rate. My mother has no source of income. I will be paying off the loans. I have a sister who is married. How can I make sure that there is no claim from my sister on the property in future. What sort of documentation or declaration I need to take from my mother/sister