I haven't read all the replies, so forgive me if I repeat something...
IMO, $1000 for a horse with problems, ANY problems, is too much in this market. Granted, there have been occasions that I have bought horses that were overpriced because *I* wanted *THAT* horse... but I was well aware that I was NOT getting a 'good deal', price to market wise. So, if it ends up that this IS the horse for you... only you can decide if $1000 is a 'good price'.
I would have a vet check....with good Xrays of the hooves. Sure, horses can recover from founder (but are usually always more prone to it again, depending on the reason for the founder), but not all founders are alike. There are certainly different degrees of founder. Some quite recoverable from with the right care and knowledge, and some that permanently 'disfigure' the bones within the hoof. If the horse is truly recovered, there won't be any abnormal rotation of the coffin bone, there won't be any 'ski-tips' on the coffin bones, there won't be any significant deterioration. You cannot tell these things without Xrays... you cannot tell these things from the way the horse moves or doesn't move. Most horses are quite 'noble' creatures, and attempt to mask pain/lameness until they cannot anymore. (in the wild, lame horses will be run from their herds as liabilities)
Pain indications might be subtle enough for a newbie to completely miss...not understanding what they're looking at...
At least is sounds like the seller was honest... so far. (just don't assume there's something STILL NOT being unsaid)
Another thing I'd like to touch on is this...
Many non-horse people, or those new to owning horses, are under the impression that one trains a horse... and the horse is trained. There. Done. Well broke, trained horse. Forever.
This is SIMPLY not the case... at all. Now, there are VERY FEW old souls that are far more honest than others that this MAY be true for... in a way... but 99.9% of the time, this is NOT how it works....not at all.
There is no such thing as a trained, finished horse that'll remain that way no matter what. You can find the safest, calmest, most well mannered animal that is superbly trained... and in a month...six months... a year... have an entirely different beast in your pasture. This isn't necessarily because the HORSE suddenly 'went bad'...
It's because EVERY single second you spend with a horse... not just riding... but feeding, petting, leading, riding, handling in ANY way... every single second... you are TRAINING the horse. For it's entire life. Really, every second. Or... in MANY, MANY instances with inexperienced or new owners... you are UNTRAINING the horse... or rather, retraining it to be a very bad horse in many instances.
Unless you know how to properly handle, ride, and reprimand the 'perfect horse' (and know what things need to be reprimanded), you will soon NOT have the perfect horse anymore...
You are ALWAYS training... or UNtraining. Always.
And you really should understand 'horse language' and herd hierarchy (even if you own just a single horse...YOU are part of the herd) to even begin to know how (and why) to properly handle them. Or even...when THEY are slyly handling YOU instead of the other way around...
I'm not saying any of this to deter you necessarily... just to make sure a prospective new horse owner KNOWS what they're getting into. So many people even want to train them or handle them almost like a big dog... with the same tactics or under the impression that they even *think* the same way. They do not... in fact, nearly completely opposite in many ways. (one must understand that a dog and a horse have very different places in the 'food chain' even...one a predator, one is very much prey and THINK and react exactly spot on for their 'food chain' status) Many people...that some less experienced people may even look up to as knowing a LOT about horses...as even 'good riders'... don't even have this concept in their tool box...
When you find the PERFECT horse... your very next step should be finding the PERFECT mentor/friend/trainer that actually knows...truly...what they're doing-- and even better-- is good at teaching someone else how to handle any given things that WILL pop up. WILL.
Sounds easy enough (ha!), but I'd hate to be a newbie trying to decipher who knows what they're doing and who doesn't... As a lifelong horsewoman, I've seen far more of the latter... in ALL levels of actual riding skills. It'd be a daunting task to find a good trainer/mentor if I didn't know what I know now... especially because even the very worst can, at least initially, make themselves SOUND like they know what they're talking about... ugh!
Anyway... I do hope you find what you're looking for and are extremely happy with it... just be wary of buying 'problems'. It IS true that this is a buyers market...and there are some amazing 'deals' to be found. In OUR area (not knowing where you're at...) a $1000 aged horse with past or current problems? NOT a deal... not at all. HOWEVER, like I said... sometimes it CAN be the *perfect horse*...you know you're being taken for a ride in the pocket book... but it doesn't matter because you WANT THAT horse...that specific horse. It happens...and, at least to the buyer, it's "worth it". Yes, you could get another horse for even half the price (or less) that, on paper, is exactly the same...but no two ARE exactly the same...and sometimes, you do have to have THAT horse...