This building can be commissioned from Robin the Carpenter at a cost of:
10000 Gold + 100 Hardwood + 5 Iron Bars
It comes with a horse included, which you will be allowed to name upon completion of the building. It is recommended that you build the stable near your house for easy access with at least a 2 block wide pathway to enter and exit since the horse cannot travel down single block pathways (near (above) the little pond on the right is a perfect spot). Once you get used to the faster walking speed the horse grants you, you will never want to walk on foot again. The horse stays outside of any establishment you may enter, as well as the dungeon and does not wander off. It will eat grass while it waits and will never abandon you. If you leave it out of the stable at night it will reappear there in the morning. You do not have to feed or water it; it's a maintenance-free ride.