I didn't mean money was the only thing, just in addition to what the above was saying. My cousin had always wanted a horse and when my grandma got her one for Christmas she loved it very very much. That horse was her ONLY friend, she is sort of one of those recluse sort of girls that everyone at school made fun of. Anyway, she vowed to never ever sell Fancy and she never did. However she never had the money to take care of her. Her hooves grew too long and she rode her anyway. The horse was only about 14 hands and yet she gave it enough alfalfa and grain (because the horse liked 4 way grain) to feed a working racehorse! The horse went lame with a bowed tendon, the vet was never called. As soon as she was walking without a limp she started riding again "she's not lame, she's not limping." Fancy ended up with a permanent limp. Then she moved the horse to a place where she had nobody to ride with and the horse was in a 10X20 stall. Because she was alone she wouldn't ride her...and yet kept up the feed rations "because she's hungry." The horse got fatter and fatter and eventually foundered and died because when it got sick, "I can't afford a vet."
I tried to step in and offered to pay full board for a stable where she would have people to ride with (and hopefully help her see the light) but she refused to take her to a stable again (she swears the SO of her last stable caused to bowed tendon).
Now it is about 10 years later and she has been doing her homework, researching horse care etc in the hopes of getting another horse and the other day she asks "do you think I contributed to Fancy's death?" I think she's finally getting it.
So this is why I posted that you need the "means" to take care of a horse too or at least the knowledge that if things happen down the road and your situation is no longer favorable for the horse, you need to find it a home that can. There are a LOT of people out there like my cousin who believe in the "forever home" and that is a really really good thing in most cases, but sometimes it can go wrong.