Sometimes you have to make your own.
We just bought 10 acres in Azle, it had a couple of horses on it before, but it wasn't a horse ranch.
I've spent the last 5 weeks rebuilding fences, setting cross fences, running 600 feet of water pipe to 5 pastures, clearing brush, moving felled tree's, lining run -in's with lumber. This is phase one - "operation horses home" LOL. I've been given the all clear to bring our horses from stabling next Thursday by Mrs Pony. Next plan is to build a new barn - the old one is kinda small.
My wife is pulling double shifts, and I am working full time here to get it ready. Something rewarding about working your ass off in 100+ degree heat for 12 hour days, solid for the last 5 weeks, and then looking back with folded arms and saying "I did this". Not bad for a computer programmer by trade
I guess what I'm trying to say is find a nice property, you can make it a horse ranch afterwards.