Being a paralegal in training, I wouldn't even consider something like this without legal help first. Sure, you can get a LOT of things online such a boarding contracts and so on, but what about state specific statutes that apply to boarding facilities, do you know where to look for those, or even how to apply them?
I know that you say an attorney isn't out of the question, which is good. You need legal help. Even if it is just to get your P's and Q's in order. No competent attorney's in your area? Then search outside of your area. My suggestion is not to go at it alone, yea, legal fee's suck now, and you probably don't trust an attorney as far as you can throw one, but think about how much you'll need an attorney (and appreciate legal fee's vs. thousands of dollars in damages) when something happens at your boarding facility?
Also, I like the idea of having everything taken care of before you start letting people on. Sure, it sounds great to start as soon as possible, but in my opinion it's kind of tacky to just add things here and there. Wait.. That kind of sounded snarky, didn't it? I'm sorry, If I were to go to a barn who wasn't completely set up, I'd start to wonder if maybe boarding was just an after thought, or just a hobby, not a profession.