I have a horse. Owning a horse is not for the timid!
There is as much to learn about horses as there is about GSDs. They require vet care twice a year (shots, etc). They need their feet attended to by a ferrier. They need de-worming. They will keep each other company -- no horse should ever live alone. They are frustrating and wonderful. They are crazy and noble. They are scardy-cats and brave. They are a pain and a joy.
Start your education with books, videos and websites. It would be best to find others in your area who have horses you can hang out with and learn. Find a trainer who will teach you how to ride YOUR horse. (It takes time to build the communication with an individual.)
There is absolutely nothing finer than having your horse in your back yard and 5 miles is pretty darn close!