We have a dedicated field here in Mission BC. It does pretty good, but the property is owned, not leased and the home of the owner is located on the same property.
It took 6 years to build the player base, we now have a pool of about 120 with 40 to 50 showing up for the bi-weekly games. Field fees are only $12.00 for the day, but that is extra cash for them.
I think if you work a solid business plan you find, unless rent is dirt cheap, it will pretty tough. You can supply bb's but you will not make a lot on those, as well as a snack bar etc.
Rentals work out good once they are paid for, our field rents at 50.00 for the day field fees, mask and bb's all included. All the rental guns are beta Spetnaz ak variants and have been running good for about 4 years, currently there are 12 available.
But if you need staff to run things your costs will climb fast.
Field costs can not be too high or you will have no player base as people won't shell out.
But even at $20.00 per head for the day, and say 30 players you only make $600.00. And you will not get those numbers every weekend unless you have a high base player count.
Remember paintball is messy and starts to limit your options for other things like, laser or nerf games for the younger crowd.