Rescuing is WONDERFUL if you have experience. Most rescues evaluate their horses so you'll know what each horses experience is... I pulled 4 horses from the kill pen oct 08 and all 4 had training issues lol. Theyre all wonderful riding horses now but it took a long time to get them all there. Most rescues ( MOST ) are there for a reason as mean as it sounds. Very few are well trained. There ARE well trained horses going thru the auctions latley though. Just take your time and find something with a lot of backround info with a comfortable training level for yourself. Don't get in over your head b.c you fall in love then its even harder to try and re-home or part with the horse if it dosen't work out. Keep your eye on craigslist. Lots of cheap NICE horses for adoption/sale latley. Good luck let me know how you make out!
Anything that is free or cheap get it vet checked. It may be cheap because the market is bad but there is usually something up with them. No point thinking you've got a good deal to find you've actually got something that requires ten ton of money pouring into it to get it sound for riding. Actually get any horse vet checked but especially the cheap/free ones. And before people start going "oh well I got my horse for free and they're great and always have been", yes I know you can get them but they're not the norm.