Good idea.  Unrealistic, but good.  That's a few hundred thousand dollars startup (minimum) not to mention full time staff to maintain it, clean it, manage it, and then we have to charge an outrageous amount of money for anyone to show up just to stick around which kind of defeats the purpose.  That's a full-time project for someone who's only goal is to open an athletic gym, and the chances of an only-parkour gym in Boise, Idaho surviving are less than great.

~~Jack, Idaho Parkour

There was an article on the APK home page of someone doing this, I believe in Toronto.  He gives a good video tour of the place.  I would check that out first to see what he did.  It was pretty basic from what I remember, so it might not be that expensive.  But I wouldn't quit your day job for it.  I kind of like the idea of starting something like that. 

You would probably need enough people to rotate work there to supply money from else well or maybe do a membership thing like the archery place in Nampa does.

For some estimates on cost depends on what you want to build.  But this might give you an idea.

http://www.tiffinmats.com/index.html

Have you thought about starting a 'class' at one of the local gyms?  I know that at the Nampa Rec Center, there are a bunch of classes that meet periodically.  If you could get in touch with one of the managers there, I'm almost positive that they would love to offer another class.  Also, I am willing to bet that the costs would be fairly low - just a weekly renting of certain parts of the gym (ex. gymnastics area for general practice, weight room for strength training, rock wall for the obvious, or the pool for recovery and technique practice) and passes for the members.  The passes would probably be around 30 bucks for a month, maybe less.  I know that the rock wall passes for the upcoming event (Jan 26 - March 7) are $27 for people without memberships, so it shouldn't be very expensive.  If you need more random ideas, just ask.

It's a good idea, however... Idaho just isn't the place to do that.
You'd have to wait a few years for parkour to become more well-known, and even then, most idaho traceurs would leave to go elsewhere where there's more traceurs. lol.
Idaho is for rednecks and richies, don't waste your time.

Try Portland, Oregon, lol

there are a bunch more guys over there that are into it but from what i know there are already more than a few places there that run classes and stuff out of gyms they own.
they don't post a lot on here, its kind of just word of mouth in whatever towns have gyms and classes