If you are looking at a franchise opportunity you should read this article from Barry Kurtz on Digging into Franchises:  The Due Diligence Minefield.  His proposed Legal Due Diligence Checklist within the article is a must read. 

The due diligence process is important when buying a franchise (or any business).  Kurtz’s article deals more with buying the entire franchise company but the article is helpful even if you are buying a single franchise.  I also have multiple articles addressing due diligence issues when buying a franchise including:

Joe Cooney and I have a podcast on Buying a Franchise Basics which also has some helpful hints on franchise due diligence.  Joe has some great insight so I recommend a listen.