Welcome to the forum Sean!
FZS 600 is so good bike I cannot find any fazer specific issue that you may look for.
There is the famous front sprocket nut change, but honestly we have not seen any foxeye with real problems there. And if yours is old 9mm nut, the change is £6 to get the new 12mm nut.
Obviously look for general abuse, crashes, bad maintainance etc, but these are general things you look when you buy second hand.
Check the suspension, head bearings etc.
Obviously try to get low mileage one.