REPLY: Know what I've learned along the way regarding buying a horse?: 1) always get a vet prepurchase exam (always!!), and 2) if you can, have your favorite farrier have a look at their feet before purchasing as well. They can see stuff we might not and advise you on how well they think the horse will transition to barefoot and how long/short that will take and how good their feet are in general.
Most horses transition just fine to barefoot, but with varying degrees of sensitivity, individually. My own horse, Sundance, that I bought this time last year had always been shod by past owners, for 11 years, but the first thing I had my farrier (who also works at the vet school here) do when I got Sundance home was to pull his shoes and start focusing on trimming him to be barefoot. One year later he's just fine with that, except he is a little bit sensitive if you walk or ride him over gravely roads. But most barefoot horses are there, I find. But since I don't ride my horses on gravel if I can help it (there's always grass next to any gravel driveway or road!), that's not really been a problem. I kind of look at it like this: if I wouldn't be comfortable walking barefoot on something myself, I wouldn't ask my horse to either. But you might have your farrier have a pre-purchase look. Can't hurt.
By the way, my farrier here taught me one cool trick to do when you're checking out a horse to buy, to make sure no one has done a nerve block on the horse's legs/feet before you arrive (hiding lameness). Reach down and press your fingernail hard into right where the hoof attaches to the leg, that intersection "crease." If a horse has been "numbed" there medically (drugged there/nerve block), he won't feel a thing and won't react to that when you press your fingernail hard in there. If he's not been "tampered with" there, his leg will "jump" at that fingernail pressure right there. I had no idea this nerve blocking was such a big problem out there, but apparently it is, especially at horse auctions, where they try to sell lame horses to clueless people. So, that handy little foot test is good to know!