Join Date: Jan 2012
Location: Calgary, AB, Canada
Decide what you want, then pick a horse accordingly.
If you are very ambitious about riding (and that's what it sounds like), this mare might not a good match for several reasons.
For one, it sounds like the mare has several health issues (hock arthritis, old tendon injury, "ouchy" front feet). This might not be an issue if you trail ride a bit, but from what it sounds like, you are looking for a horse that you can work a bit harder. Especially cutting is hard on the joints, so you might have issues with unsoundness soon. If you do free lease her, make sure you get an independent vet to evaluate her beforehand, and make a contract that lay out what happens when she goes (permanently) lame. Will she be paying for vet bills and medical procedures like hock injections etc if needed? You don't want to be stuck paying for a horse you can't ride, or the owner accusing you of having lamed her horse.
Secondly, it sounds like this mare might have some training issues. Nothing major, she might have a good attitude, but having sat for a long time she will be out of shape. Nobody here will be able to tell you how she reacts to a lot of intense work. Some horses are happy and thrive with a lot of work, some - especially when you push them too fast - become sour. Also, picking up canter leads is something pretty basic and suggests that she doesn't have a ton of (professional) training on her.
With the health issues, and the questionable training, I think if I were you I would pass. If I were ambitious about getting better, I'd look for a horse that is sound well trained, and has a good character, maybe with a bit of scope to move up.
If you decide to lease, even if it is from a friend, make sure you have a good contract in place that defines both your and the horse owner's rights and responsibilities. It should include things such as financial issues (e.g. who pays for board, feed, farrier, supplements, tack, routine and emergency vet visits?), but also organizational stuff (e.g. what is the procedure to terminate the lease? Can you take the horse off property, to lessons or shows? Who makes decisions about tack, farrier and veterinary care?).