Do not buy any horse that is prone to cribbing. This habit is almost impossible to cure and other horses that you have can pick up this bad habit, which can lead to colic, weight loss and overall bad health. After you purchase this horse, the very first thing you should ask is what type of feed that the owner is currently giving this animal. A sudden change in diet can lead to colic and you could be looking at a big vet bill right off the bat or the horse could die. If you are not sure, while you are having the vet check the horse over for soundness ask him what he would recommend to feed this horse.
Every area has different types of hay and grasses.
If the previous owner fed this horse oat hay, then you should feed this horse oat hay at least for the first two weeks. You can gradually change the feed to alfalfa or Timothy hay over a two week period for instance. Check with the feed store to make sure that the hay you are buying is horse hay and not cattle hay. Horses can not eat moldy or bad hay, but cattle can. Also see if the previous owner fed the horse grain and how much.