*I am a boarder, not a barn-owner.
It depends on how you allocate the money. There are various expenses.
You can have a barn food, treats, vet, farrier, fly spray, toys, tack, etc..., or you can have people use their own. At my boarding barn, the boarders have the option to use the barn's, but we can also use our own, or mix 'n match.
Farm supplies include tractors for cutting the grass or raking arenas. They also include rakes, pitchforks, shovels, fans, water heaters, mats, etc... We have barn-provided farm supplies; nobody uses their own.
Fencing. Some barns have a "you break it = you fix/pay for it". Some don't. At our barn, if our horse breaks a fence, we have to manually fix it, but we do not have to pay for it (the supplies).
Grounding/footing. This includes sand, gravel, sand/lime stone, etc... We have a sandstone drainage in the pastures which gets delivers every few months. We do have to pay for that, but we do not have to spread it.
"I wumbo. You wumbo. He- she- me... wumbo. Wumbo; Wumboing; We'll have thee wumbo; Wumborama; Wumbology; the study of Wumbo. It's first grade, Spongebob!"