A guy I know said a great thing the other day (he owns and runs a boarding facility): "I never realized it, but when I built this place, I married it".
It is very true. You have to be prepared to put the hard work in every, single, day. Including Christmas, during your best friend's wedding, during your friends' summer holiday adventures, etc.. etc.. You will be at the farm, taking care of the horses.
Not to mention the financial commitment and the fact that just to break even running a boarding stable (let alone making a living!) is next to impossible. I don't know of one barn that makes enough money to put food on the table. They all have spouses or parents supporting them with a "real job".
So good luck! But it is not the fairytale life you are dreaming of...
They say money doesn't buy happiness -- well happiness doesn't buy horses!