Maybe if you are very careful, very lucky, keep your horse barefoot, and have no interest in any lessons.
Not really though, IMO. I don't really want to tally up what I pay for my horses, but I take 4-5 lessons/month at $30 each ($120-$150), ride in the arena 4x at $15/each ($60), then you need farrier work ($25/trim or $50-$100 for shoes). My hay runs me $50/month at least (but was more like $150/month during the drought), supplements $50/month, then there's vet bills, worming, vaccinations, gas for the truck and trailer, tack, consumables like treats, fly spray, conditioning sprays, and wear and tear on facilities, etc. I have my own property, so I don't even have to count board. You really do have to have a decent emergency fund as well. I have spent about $1500 at the vet in the last 3 months and am also paying for specialty shoeing. Note that I do not have any show expenses listed as we are not currently showing. If that's something you want to do, you have to budget hauling fees or gas, plus all the entry fees for however many shows you want to do.
Tug on anything at all and you'll find it connected to everything else in the universe.~John Muir