Hm, having lived/worked/boarded in the Seattle area (Kirkland) for a few years, I would not say it was budget friendly… that was several years ago, but as a right-out-of-college young adult, I really struggled financially out there.
You want to avoid VA/DC/MD/NY/CT/MA for the most part too.
I lived in TX for awhile, it was fairly affordable, but too hot, and the H/J availability around where I was was pretty much 0 --we had to haul 3-4 hours for even a schooling show.
I live in NC now (southern pines area) and it’s not bad penny-pinching wise, and wonderful in all other regards. Board wasn’t the cheapest when we scoped out commercial options (ended up buying a farm and doing it ourselves), but there are so many shows and horse things around; the accessibility to good vets, farriers, shows, clinics, etc is unmatched and wonderful.
Probably the most bang for my buck was Ohio (Dayton area). Board was very reasonable, especially considering every facility needs an indoor. Several shows at all levels (A, C, and schooling) every weekend all season long within an hour or so, and KHP and Rood Riddle still very convenient. You have access to some great trainers and show barns (David Beisel, Lindsay Yinger, Lochmoor, etc) and some smaller, decent mid-level barns as well. Winters suck, but I really felt like my paycheck went farther there than most other places I’ve lived.
I didn’t love Ohio, and we LOVE NC (enough that we bought our forever home, and plan to retire there permanently in 12-15 years when I’m done with the military.)
I think it can be tough to find a balance between affordable and still have access to good programs, qualified vets/farriers, and access to good shows. Remember to research things like average seasonal temperatures and rainfall. Also commute timelines are important to look up. It’s no good to have the perfect, affordable barn 30 miles from the city if it takes you 2 hours Each Way to get there (ask me how I know).
Try to spend some time in an area for awhile before you commit to it – or at least visit for a week, scope out properties and barns, and talk to the tack store clerks --and make sure you have a convenient Whole Foods or Trader Joes nearby :-).