I'm in Texas, but just to give you more information:
I keep my horses at home. Per horse this is the expense:
Monthly feed & hay cost: $100
6 week Farrier visit: $35 (no shoes, shoes are $65 and up)
Annual Vet Cost: $150 (split farm call)
Equine Denistry: $100 and up as needed if done by a specialist; by the vet it's cheaper
Equine Chiropractic: $100 and up as needed
Supplements vary per horse. Some don't get any. The initial cost of just brushes, shampoo, halters, and tack will add up fast.
We also provide boarding services for others at $350 a month which includes the feed, hay and wormer. Everything else the boarders pay out of pocket. Ours is all inclusive so we'll meet with the vet and farrier, and we blanket and unblanket horses, feed supplements, etc. Some facilities around us charge additional fees for these services, so if you're boarding, the extra fees are something that should be looked at closely as they can blow your budget.
You really need to think about what it will cost for vet services in an emergency. I lost my mare a few months ago due to Torsion Colic. The vet couldn't treat her at our place so I had to bring her in (meaning you need fast access to truck and trailer sometimes), and later had to transport her to an equine surgical facility (at 1am so again, you need access to truck and trailer). We didn't opt for the surgery at the end (min cost was $6,000 max cost was $14,000 with a very poor prognosis) but the cost for the two veterinarian services was over $1200 just for the pain meds, blood work, ultrasound, etc. Sometimes a colic episode can be as little as administering some Banamine, and sometimes it can be as severe as what my mare went through.
Something you can do though, if your horse qualifies, is buy horse insurance. It helps defray the cost for colic surgery and major illnesses and injuries.