What
@Odd Job said.
On ventilation, figure out the dead minimum and double that, just a s a working number. Really what you want is one system for the lobby/check-in/sales floor area, and a separate system for the shooting bays. Your best bet in the shooting areas is to supply air at the shooting end, and extract it at the target end.
Now, this may be met with resistance by some HVAC contractors, as it's not 'typical' commercial work.
Especially the part where the shooting line really needs constant airflow, whether the air is conditioned or not (you may need a multi-stage blower, but constant airflow is virtually a given.
Also, plan ahead for what happens when you change filter elements. Which includes things like lead time for replacement filter media, as well as the physical time needed to make the change. Having to shut down the range to change filters is not to your financial advantage.
Consider a sloped floor back to the line from about 8-10 feet out, feeding back to a broom-wide tough to catch empty cases.
Consider a line design that does not let the public beyond the line at all, and a separate employee-only access to the back of the line. That access point ought to be given a camera, and be opened by external command, preferably by some one able to see the range.
Add More Light. A dim range is a pain. Have specific task lighting for cleaning the trap ends (another task made worse by not enough light).
Consider if you want to be able to "scale" lanes in use. Let's say you have space for 16 lanes. It might make sense to make those 4 groups of 4 each. for slower days. Or to have the magnums split away from the rimfires.
Oh, and spend more than a little time looking up the info for running a business in your area. Reach out to successful businesses and ask them about pitfalls and recommendations. You probably need a sales tax application from the State, which may require you have your City Business License squared away. Having the City license in hand may (or may not) require having a commercial bank account (that commercial line of credit can be very handy, too). You probably ought invest with a local business attorney, too--there are very good reasons to be various variants of limited liability business entity, whether sole proprietorship or corporation or the like. And local conditions vary on those.
There's another snag you may hit. Zoning may not preclude an indoor range, but the required Occupant Load can make the parking area required complicated. Existing parking may require getting shared parking agreements with nearby businesses. Making parking lot changes can come with wacky landscaping requirements, too. Which can be deal breakers. Accessibility will also be an issue with adaptive reuse of an existing building. (Note, employee access is not exempt from ADA.)
