<prompt> Human: So I ve lived with my roommate for a little over three years now and he has become like a brother to me. He currently has really bad credit due to circumstances beyond his control. Hes been working on improving his credit for the past year. Anyways we are looking for move into a new better apartment but they do check for a credit score and although mine is excellent, his isnt. So anyways I wanna help him build his credit. If I make him an authorized user to one of my credit cards, would it harm my credit score? I cant seem to find a solid answer online.  <response>: Dont mix your finances unless you are married. 