It's so good of you to save this horse and take the money to fix him up. He might take a while to come around (or maybe starved for affection and come around immediately), but it's always worth it in the end to know that you gave them a good life, even if for a month to many many years.
I have no idea how people can do these things to animals. I have rescue animals at my house and my grandfather has a cat sanctuary in the mountains of northern NM. It upsets me how outdated laws are and some of the things that the HSUS have as "guidelines" for animals - some places personality test the animals right when they come in, before they get to eat or drink or anything. Of course the dog will be good aggressive if he hasn't seen food in months and has been eating his own waste. Then they deem them unfit and put them to sleep. The dogs who do pass the test, the HSUS says should only be given 3 days to live in order to not spread disease and make room for other incoming animals. Again, these are guidelines that most shelters don't follow as such, but one in my town follows them to a T and ticks me off so much! It's all an issue of space.
Animals aren't seen as living beings with a heart and personality. Horses were cars, cats were rodent killers (or witches' familiars...we won't even get into that horrible practice), and dogs were guards. I had recently asked a question about liability insurance and such because I'm interested in becoming a veterinarian and am changing my major. I was wondering if the malpractice suits and such were as much as regular doctors. The answer was horrible, but true - the people will only get as much as that animal was worth in terms of property - $100 or $1000 or whatever. To me, that's horrible. Good for vets so they can't be killed and scared away from the profession by malpractice charges, but in my opinion, morally horrible because in my house, all of our animals are family. They can't have a price.
Sorry for the tangent, but these things upset me a ton. If I do take the path of vet, I want to do an internship at Best Friends sanctuary.