I have one cat in the barn. She adopted us at our last house. We started feeding her. I often get "presents" left for me. She gets wet food sometimes (usually when it's cold out, or if I feel nice. But she gets dry kibble otherwise. Just a small cat food can worth of dry kibble. One time per day, in the evening (usually we lock her in the barn at night, and every 8ish weeks she goes to the vet to donate blood, so we keep her on that schedule so I know exactly where she'll be in the morning when I pack her up
Sometimes she is very needy and will mewo at me annoyingly. Usually though, she's a really good kitty. When she gets annoying, I put her outside. She scouts out the creek at the back of the property, and we see her carrying things in her mouth. She eats rats, if she finds them, and sometimes voles, but usually she just rips things in half and leaves them for me.
I was at a barn once that had like 8 cats. You had to hang blankets, because they would pee on them if you just folded them up & lef them on your hay or bench. That many was really annoying. They also had huge dishes of cheap crappy cat food, which I think aided them in being lazy.