I think if a rescue is what you have in mind...an auction is a great idea. There are many local livestock auctions across the nation that have horses in need of good homes. Some are in rough shape...others are not...but they all could use a good, safe, permanent home. The risks associated with auctions include purchasing an unhealthy animal (which could be costly or heartbreaking) or purchasing an animal unsuitable for your level of experience. If you spend a bit of time with the horse prior to purchase and watch it carefully for a suitable temperment for yourself and your needs, I think that the benefits would outweight the risks involved...especially since you are just looking for a buddy horse rather than a show/riding animal. If you were looking at an auction for a riding animal, I would take someone with you who was knowledgeable of horses temperments, the local sellers (if possible), and conformation to check for soundness issues. Sounds like you will give a horse a great second chance at a happy home.