I'd start saving NOW and make a plan for what you want to do and how many horses you want to have. I'd also look for an area that is horse friendly with lots of trails, training, local shows and riding groups. I miss that out here!
I wouldn't have any less than 20/30 acres and 40 would be ideal so you could cut 20 acres of your own hay. I personally like river valleys with great pasture. Throw in a nice barn and a home for you of course and that equals Heaven!
I'm east of you in AR but in the "mountains", there have been tornadoes around us but we are nestled in where it's a tad safer.
There is a BREATHTAKING little farm down here that we tried to buy. But the people didn't want to sell. It had 65 acres, nice southern exposure but nestled on the north side of a valley, well fenced with wood railing, nice small horse barn, immaculate rich pastures, cute house kinda 70's but doable, a greenhouse, hay/cattle barn, and was on a NICE big spring fed creek. It was also just down the road from the National forest so there were a thousand miles of trails. We still go look at the place.
We got our place instead and I like it but I wish we had more pasture.
80 acres surrounded by national forest with good trails, cool 1910 farm house we had to gut, three barns, decent well and one original hand dug well, a cute open horse barn, loads of big timber, private waterfalls at the bottom with a nice little creek. CONS! Hadn't been lived in in 10 years so we had to renovate everything. Fencing was terrible and we are still working on it, only have 20 acres of decent pasture so we can only have 3 horses without having to feed hay year round. Good and bad is that we are on the north face of a mountain so there is a constant breeze but it gets chilly.
I'd go for rich pasture, private, no neighbor horses, sunny south facing property, fresh water and good wells, sturdy fencing, established trees for shade, nice barns, and a workable home. You can always fix up a house, you can't add on good pasture! As far as location... I think Tennessee, Virginia, the Carolinas but they can have tornados too... Maybe Colorado or Ohio? Ohio seems nice especially near the mountains.