When I was in the Army, I found that there were always facilities on or close to the base for horses. I never had to go more than ten miles to find a place to keep a horse.
As for how to find a place that you can trust - it is HARD. Go out ad talk and talk and talk and look at every horse on the property. If you don't love how the hroses look, walk away. If possible, find and talk to other borders and find out what they like and what they don't liek about the place.
Take a look at the feed. TASTE the feed. If you don't like the taste, why would you expect your horse to?
If you get heebeegeebees for any reason, walk away.