Please, always remember, horses in the wild know how to take care of themselves. They have the option to move to areas that suit their needs, such as they can go into heavily wooded areas to escape the hot sun as well as the driving rain. If there is too much water on the plains, they can go to higher ground and so on. When we put horses in a pasture, we limit their movements, their ability to find water, shelter and forage for total nutrients that they instinctively know they need.
This is not to say that there are no happy horses in captivity. I have met many horses that loved their nicely bedded, clean stalls with a beautiful mound of hay in the corner and the correct amount of feed in their feed tubs, as well as one or two buckets of fresh clean water. Believe it or not, horses would much rather prefer cleanliness over stalls filled with manure and dirty water buckets. It is important that each horse have not only one stall per horse, but at least one acre of grazing facility if they are being fed grain and if in areas where the winter months does not grow any grass, that they are being supplemented with a good quality hay. If no grain is the option because of risk of founder or other issues, then two to three acres per horse is reasonable. Some horses or ponies for one reason or the other may need some monitoring as far as grass consumption and may have to be brought in or put into other areas for certain amounts of time each day. Keeping horses in small pens with little or no grass is not a good thing. Even if they are getting sufficient amounts of hay, you do risk the over consumption of sand which can lead to colic or impaction which could be fatal.
These are the main things you must consider for your new best friend; shelter, water, grazing, feeding and exercise. Horses are herding social animals. They want, and some need, to be with other horses. They will not always get along with each other and sometimes we cannot put certain horses together with other certain horses. Not all horses are happy just standing around doing nothing. Some horses love having a job, not only to break the boredom, but they enjoy the interaction with people. The facility that you choose should have designated areas for riding. Also, having trails near by is certainly a plus as trail riding is not only a bonding time for you and your horse, but a very relaxing one. Proper fencing is imperative as horses are inquisitive and pushy at times. Bob wire fences are for cows not horses. Bob wire can and has been deadly to horses. Choose a clean facility that has people who care about horses as much as you do, and, the further away from a road the better. A loose horse seems to migrate into traffic. Remember, having horses is a true commitment. I have always thought of them as my children and loved them as much.