There is no way to really prep for the interview. You are who you are and that is what they look for. Just know that when you are in for an interview, everyone you talk to from the front office support to random people introducing themselves to you are giving feedback on how they like you. Be genuine and convey how excited you are about the opportunity. Also, don't expect to get paid more than 35k or work less than 55 hours a week. They are never flexible with hours or pay for employees.