This question aims to understand two aspects. First we want to see if this is indeed a new position and if not how long it has been available. You are also able to investigate what career path the previous employee has taken, which may be an indication of your own future development.
Understand if Position is New: If the position is new and not an expansion of a current team with similar job functions, we can expect a less defined work environment. There are probably no procedures in place to handle potential problems. This does not agree to all people, but if you are the type that loves a challenge where every page is unwritten, this may be the perfect situation for you.
Understand Why Position was created: In case the position is new, this natural follow-up to this question is why it was created. What were the reasons behind it. Often this can give valuable insight as to what skills and attributes the employer is appreciated.
Evaluate Promotion Opportunity: If the person in this position went on to new more exciting responsibilities, this means there is an opportunity for you as well. Positions with a lot of exposure with senior management can be either a blessing or a curse, depending on how well you perform in this role. If your results are poor, then their image of you may also be poor.
Underestimating First-Mover Advantage: For some the responsibility of being the first person in a position can be daunting. It can be scary to not know whether this position has already been established as a part of the organization, but sometimes the potential gains are also substantial. Try to, as objectively as you can, evaluate the risk. What do you believe is the likelihood that this position will not exist in a few months or years? Knowing this risk you can then make an informed decision and tackle the challenge. There are also questions you can ask to help you asses this. However, start by voicing your concerns and ask how high in the organization has this position been anchored? Who made the decision? Who had concerns about this position? What were the other alternatives? This should help you better assess the risk involved.
All Interview Questions about Job Role & Responsibilities