I would go forward very carefully. Some horses always keep bucking as a option, especially if they have been "rewarded" in the past by people getting off and going home. I had a very nice paint that would come unglued when he felt like it, and those killer bucks were terrifying and painful. I put a ton of training into him over two years and he would win at the show on Sunday and then try to kill you on Monday - just because he didn't want to be ridden. Farriers, Vets, soundness exams, saddle fit - all examined and reexamined. Seems he was broke by a teenager who got dumped often and would put him away when he was bad. He never forgot that. He was the most frustrating horse I have ever owned, because when he was good he was a show-stopper. After my accomplished 18 year old had a particularly nasty fall we moved him down the road. He was never going to be a safe, easy ride. Due to his show record he sold quickly in spite of his problem (which I represented honestly with videos of his fits), but I saw him for sale again just a few months later. He will probably end up in a pasture or an auction, and for good reason - because I would put him down before I would get on him again. Just not worth getting disabled over a horse.
If you are buying him as a pasture pet, then that is great. But just be aware that sometimes you can rehab a confirmed bucker, and sometimes you cant.
There is no passion to be found playing small - in settling for a life that is less than the one you are capable of living. - Nelson Mandela