LeedsFan,
Insurance? Liability and contents? Will you be selling booth space, does the venue get a cut?
Concessions? Who provides and what do you get from sales?
Set-up and tear down labor? Who provides and what are the costs?
Union labor restrictions?
Utility costs, labor and equipment?
Internal and external marketing/advertising opps. Costs, revenues, sharing, set-up, tear down, content restrictions,
External vendors?
Just a few ideas. :)
Good Luck!
Source: http://www.abusinessmentor.com