We have one horse here on our 12 acres, he doesn't have a dedicated purpose persay. The fencing is old dilapidated barbed wire that im tearing out slowly and replacing with electric, for interior fencing only one strand is needed and now that he is used to it it doesn't even have to be on and he won't ever touch it. Heck one strand keept him in all winter without a charger (6 months).
I tried making small padocks that would last two or three days but found out quick that horses need more room than that to run, so now I have him in about a half acre to acre plots and rotate him every two to three weeks. I also leave six acres untouched all growing season and once winter comes in October I will put him there. The standing grass is a favorite over hay and he will pick at it all winter no matter how much snow there is.
The manure is by far the best benefit of having a horse, i mulch around fruit trees with it, and make a great manure tea that i use heavily in the garden. He has one favorite spot to manure in in the winter so that makes it super easy for me to collect.
He is broke to ride but I'm just to busy to really ride much without having a purpose to do so. I am training him to carry packs aswell and will use him for packing animals out that were harvested (hunted) in hard to reach heavily wooded areas.
Horses are communal animals and the reason I only have one is so he is bonded with me and when I go to the fence he runs up to be with me. My experience is when you have two or more they stay together and actively try to avoid you making working with them much harder. Plus I found my 12 acres which only 8 are used for the horse is perfect for 1 while keeping brought in hay to a minimum.