Zoning restrictions may prevent keeping horses in some areas. If you want pasture for your horse, you need 1-2 acres for pasture, housing and exercise. Pasture is good for horses, but it's not essential because of what we know about feeding. Many individuals keep their horses at boarding stables for the broad range of services they offer. Naturally, there's more cost associated with a full spectrum of services.
Horses require forage, either as pasture or hay, in their daily diet.
In some situations, especially when doing intense performance activities, they need grain or a concentrate mix. They also need trace-mineralized salt and clean, fresh water. They need shelter from both cold and heat. You can provide them a clean, warm, comfortable place for resting with proper bedding materials. Routinely they need their hooves trimmed and may require shoes for certain performance activities.