does a loan need to be paid off before we make a creative offer?

[DJ Cummins]

The wife and i are looking into purchasing a business.  The current owner is willing to 100% owner finance for 3 years.  We are very excited about the deal, but i have a question.  I didn't ask(wasn't sure if it was to rude on a first meeting) but i am pretty sure that he still owes a bank loan on the property(probably a small amount, but an amount none the less).  Does this need to be paid off before we negotiate and/or make an offer?  Only real estate we have bought in the past was the traditional 20% down, so this creative strategy is new to me.  Owner has owned it for 20+ years, and is now in his early seventies and ready to retire.

Any advise would be greatly appreciated!  @Ben Leybovich @Brandon Turner.  I bought both of your books and/or pdf's...any advice to chip in here :)