I know a few guys that ran a fairly successful paintball field, without a lot of overhead. A suggestion would be to keep your store, and your field separate entities. If your selling guns in a shop then saving money on rentals wont be an issue. I guess I'd suggest classic army for rentals. They are built fairly well, and easy to attain. Also they don't cost a fortune.
Very important about airsofters. They don't like getting paint on their gear, so keep the fields separate. This is also an issue that hardcore has. Serious airsofters don't want to play with kids, running around in camo pajamas shooting high caps, and not calling their hits. True airsofters are the ones with the real money to spend as well. If you make a really detailed, interesting play area, you may attract more of these. To get them to play there regularly, offer discounts in store, for guys that buy a membership.
Try hosting events. This will bring in more revenue, and attract higher caliber players. If the event is big and crazy with a lot of effort put in, people will travel further to attend. Mason Relic for instance has Pyro (professionally done of course), huge draw prizes from them and their sponsors, large organized objective based milsims, and military vehicles. This will be a bit much for 25ish acres, but airsoft has a lot of effort and expectation.
I guess you could have team tourneys as well. Have your open to the public days, where anyone can come try though. Often times you will snag a player who will invest more into the sport that way. And have your team days, or for age verified more serious players.