Great question. Family is great but there are times when getting away from them can be beneficial for everyone. A new agent needs training and mentoring. They need to be in a place where someone will direct them and hold them accountable for following through or they will end up like most new agents within two years, doing something else.
Whether your sister would go out of her way for you, or just assume you know what your doing because your licensed is not something we can know. She may go out of her way or be threatened by you.
Interview in some other offices so you can make a more informed choice. Best of luck, I hope you make it.