I was going to ask a similar question as I am considering bringing a cat or two to the place I am leasing (with permission from the owners first, of course). I imagine if the tack room/barn has fresh food and water and you give them attention when you're there that they will kind of just chill around the barn and do their own thing there, but how likely is it they will take off and not return? I've considered adopting these cats from a shelter to give one or two of the shelter cats a home and it would be awkward for that cat to run away, if you get what I'm saying. :P
Also, what are all the benefits of having a barn cat?