I think the thread on members that have high lead levels is the best for you to read.
It started with someone getting a test. They were trying to figure out what was causing and decided to stop reloading. No effect. They stopped shooting indoors and their lead dropped significantly. A few others had themselves tested along the way and the general trend was those who shot indoors regularly had high lead levels while everyone else was OK. I didn't save a link to that thread.
There are many other hazardous chemicals in the mix.
I was looking at opening an indoor range before reading it and decided not to after.
Clean bathrooms. When I was doing a little consulting work I came up with a quick and dirty test. I'd find a way into the bathroom. If a manufacturing facility than the wage earner/floor bathroom. If it was a mess I'd avoid the place, be sure I got money up front, etc. If it was clean I'd be a lot more open to terms. Not because I was going to use the restroom, but because it reflected the attention to detail, pride in work, and general class of those in the business. I haven't found a place with more than 2-3 employees that the rule doesn't hold.
If you want to keep the "riffraff" out then make a membership that has high up front cost with a steep discount.