I love the idea of a new place in the Des Moines area. I actually built my own woodsball field, and got a lot of help and great info here. I have a few ideas I'll throw out there. Hope it helps.
Turf- I understand that turf is expensive as hell, but it'd be well worth it. It's great for comfort, safety, and I think it just makes for better all around paintball. I don't know what your fundage situation is, but you could raise prices a little to help with the cost of turf. Sure people will ***** about higher prices, but people would ***** just as much about not having turf at all.
Make something parent friendly- I see it all the time. Parents that take their younger children to play paintball, and just sit on a bench looking bored as hell for hours on end. Give them something to do. Free WIFI would be great. Maybe a lobby with a large tv?
Multiple fill stations- Waiting in line for air sucks. We've all done it. I think there's been times I've spent as much time waiting in line as I have playing. If you can, use multiple fill stations in the staging area. That way, players don't have to wait as long to get their air filled. I suppose you could invest in a compressor of some sort, and possibly even have self serve fill stations. I'd have someone supervising this of course. Personally, I would have free air all day, and charge for co2. I'd have hpa tanks available to rent, and charge the same price to rent one as I would a co2 fill. Or just get rid of co2 altogether. Hpa is just all around better for your marker. It's consistent, and way better for your markers internals.
Be sure to change the field set up often- I've been to places that have never changed their field set-up, and I'll never understand why? You don't have to do it too often, maybe every other week or so, but it's always nice to have something new.
Make passes- Passes are great for people that plan on playing a lot. I'd do from a month all the way up to a year. Include the field fee as well as air in the cost of the passes.
Field paint- I'd go with field paint only for many reasons. Insurance and Liability is one reason. It's going to be on the the insurance application and they are going to prefer you using field paint. I know it doesn't happen much, but if someone brings in (God forbid) Monster Balls or something that they've had sitting around for years, or something they have tampered with, and it hurts somebody, you are going to have a mess on your hands. You don't want that.
You also don't want to have all this junk paint that's hard to clean up all over your field. You're going to put a lot of money into this thing, and you're not going to want it to be all stained up and trashed because of junk paint.
I'd imagine when you clean up, you're going to wash the paint into a drain of some sort. The city is going to ask you about what you're putting into these drains. They are going to want to know what's in the paint. If people are bringing in all types of crap, how are you going to know? You've got to cover your own ***.
I'm getting tired now, but here are a few more things. Stress safety, hire helpful people, and don't let beginners play with grizzled vets. These young people are the lifeblood of our sport. Lets no discourage them from playing. I hope this all helps you out. Good luck, and I can't wait to play on your field.