She can block your renting it out if she chooses by going to court and getting an order barring that: you cannot take her rights to use and possess the home (if she chose) by renting it to another who will occupy it. Or she could go to court and seek an order forcing the sale of the house, since a forced sale and distribution of the proceeds (equity) is the law's remedy when the owners of real estate cannot decide what to do with it. You wish to consider seeing if you can buy your sister out; then you could rent it and keep all the rental proceeds. (If you did rent it out while she is an owner, he'd get half the proceeds.)