Internship offer as a full time employee

I'm looking for advice on an opportunity I received.

I currently work in an administrative position at an accounting firm and have been looking to transfer into one of the firm's accounting departments so I can start gaining the experience necessary for CPA licensure. I haven't started taking the exams yet, but I'm currently completing the accounting coursework I need.

Here's my dilemma: I'm currently a full-time, salaried employee, but the opportunity I received is to move into another department as an intern. I would retain my current salary and benefits and continue working full time, but I would technically be on a six-month internship contract that can be renewed, with no guarantee of eventually receiving an associate offer.

Would you take this opportunity to get your foot in the door, or would you keep the current full-time position and look for an associate role elsewhere?