I encourage you to pm me so we can talk in full more than I can post here.
There is a great rescue in my area called Falcon Ridge, you can look it up and get more info. They do hold fundraisers, in addition to the personal jobs outside the rescue that the owners have. There are obviously donations by people as well as sponsoring of a horse or horses, in which a person pays for the cost of one of the horses each month, until the horse is adopted out, or will pay for a chunk of say an emergency surgery for a horse, which helps alleviate the costs for you as the rescue owner. This particular rescue has also had some people donate horses to be sold not as rescues, but as good horses for a decent price that will help bring in some money. They also have volunteers that come out (they are a large rescue) and muck stalls, help work some of the horses, make sure that they all get out and get attention of some sort. Some of the problems are making sure that the horses do actually go to qualified homes, unfortunately even very well run and extremely picky rescues can end up adopting out a horse to an unsuitable home, case in point being a horse that had come into Falcon Ridge (don't have the whole story, just bits and pieces), that apparently had dropped fetlocks among other things, they thought they found a great home for him, screened the owners and everything, the horse went to the new home, and a while later it ended up at the Human Society, not entirely sure what the whole story is again, but Falcon Ridge was able to identify the horse positively in part to his dropped fetlocks, and they went and got him out of the shelter and took him back to the rescue. Also sometimes having to make the hard decision to euthanize a horse, is definitely something to think about. If you can handle it, great, but you really have to think hard about making sure that when that time comes, you can make that decision for the better of the horse, no matter what else is going on. As for training, one of the biggest pieces of advice I can give you, is make sure you have a couple other horses that you can have turned out together, either just for play time, or permanently in a pasture type situation, so they get the herd feeling, and other horses to watch, and get those manners from. And don't treat the horse like he's been abused. Expect him to do the same things as any other horse that was not abused, even though it may take longer to get the end result depending on what was done. I've heard of a couple people trying to make exceptions for their "abused, neglected" rescue horse, so they won't do a, b, or c, when the only reason the horse isn't doing it is because the owner isn't asking. Again, you should pm me, and we can have an even more in depth discussion, and I can explain things more fully, because I'm sure that some things didn't come out quite like I was thinking in my head.