You cannot run anything at 100% payback.

Some things you might need..

-Scales/ tents/ tables/etc
-Insurance, as others mentioned
-Stationaries for rules, weigh-in slips, payout envelopes etc.
-Laptop for keeping records, stats, and keeping in touch with everyone/thing...as you might know from reading alot of the posts here, your going to want to cover your ass
-Web site costs
-Hall rentals for functions
-Travel
-Monies to co-op with sponsors
-Postage costs
-Phone bill(s), yes your going to have to keep that cell phone close
-Your going to need a float to cover angler's bounched checks, misc. short falls, general payables, and possible errors in pay-out
-Trophies
-All Your Free Time

Not to discouage you. If its just a few guys out for a lark on an afternoon your fine. Anything bigger than you've got to be buisness minded.