I'm in a pricey area. Besides board, I spend:
$150 every six weeks for shoes or $40 every month for barefoot trim
$200 Spring shots
$150 Fall booster shots
$50/month supplements for weight gain, hoof health and vitamins
I pay an additional $500/year for horse insurance just in case he ever needs major surgery. I'd rather pay $500 than $15,000.
We show a little and do some hunter paces, so there's another $500 or so gone before trailering expenses.
I can't afford lessons, or else I'd be talking about another $120 a month.
A few points of interest:
1. Any time the vet comes out, expect to write a check for roughly $200.
2. You will always need a new blanket, so there's another $150 you should probably save up over the course of the summer.
3. Somebody at your barn will always show up with something cool that you will also want, so either get rich quick or learn to go without stuff.
Basically if you have a horse who doesn't get sick or get into trouble, and only ride on site and never go anywhere, you can get along fairly cheap. As soon as you want to expand your horizons, money will fly out of your pocket!
You just have to see your distance...you don't have to like it.