FWIW, it might be a good idea to talk to some of the other field owners in Wisconsin as well. A large number of folks have been involved in field operations, and can give you some very helpful information as to what to expect from running a field in this state. In the WI forum, a member by the name of strstro left a very brief comment. He was involved in BFG in Germantown. Give a call to Apocalypse and talk to Nick Skaar, who ran Dedicated in Madison, as well as Dave there, who has owned Apoc for decades. Call Mike at Stalker. Talk to Miles at CMP in Milwaukee. Get in touch with Commando, Nelson, Siege, Dave's. These are all people who have run successful paintball business in Wisconsin, and either run or seriously considered running indoor operations. The only outfits on this list that haven't done an indoor are Stalker and Apocalypse. They're the longest standing fields in the state, they don't cater to the tournament crowd, and they are outdoor only. It's no coincidence. I'm not saying an indoor field in WI can't make it, but I am saying that the business model has to be VERY different. The tournament/team guys will not be able to keep your bills paid. I'd looked myself at running an indoor in Stevens Point, right at the crossroads of I39 and Hwy10. With what a building would cost me, I figured I'd need to run 600 players per month through the facility just to break even, and that was assuming my family would work for free. As much as I wanted to run a great indoor field, the numbers just didn't support doing it for me at the time.
I took a quick peek at your IP - if you're reasonably close to where I'm at, drop me a line, maybe we can get together sometime and chat. I always like to meet people involved in paintball locally.