I just moved 3 horses home last July. Board was $425 a month/ea. So besides the initial start up costs, it is waaaaaaaay cheaper to keep them home... probably about $600 a month for everything except shows. I could keep one horse for $150 a month.
-They're close. That equals peace of mind to me.
-I know them better than ever before, quick to tell when someone's not quite right.
-Don't have any nosy boarders in my business.
-Developed better relationships with my vet and farrier, I can count on them to be there whenever anything is wrong.
-I can give my horses the care/nutrition they need, rather than what the boarding barn is willling to feed.
-I can assure they have hay in front of them all day long.
-No horse person, with more experience than I have, is close by to "consult" with. But remember, advice from a vet over the phone is free :)
-No real ring to ride in (will have one in the future though).
-Have to trailer out for lessons.
-They turned the winter field into a dirt (mud) paddock in 2 months.
-Pretty tied down to the place, feed 2x a day. Hard to go on vacation.
And worst of all, getting up early on saturdays when it's freezing cold and raining in January to go feed, when all I want to do is snuggle in bed all day
At home is a much better setup for us, hope that helps!