My 2 cents is that QRTRHRS is correct.
Most people really underestimate the costs. We sat down and figured out what it really costs us to keep a horse and it came out to a bit over $400/ month. Most folks we know think its closer to $300 until you menion all the small things.
Additionally, you have to factor in the cost of not being really knowledgable about horses.
As mentioned before I would avoid it until you know what the committment looks like.
Regards,
Mark