I have one horse I board. I work 4 days/week at a dog grooming shop and work weekends at the barn.
Right now there are only 15 horses at the farm. They come in AM/PM for feed/supplements and the BO’s show horse stays in during the day in the summer and at night during the winter. There is also usually one horse who is in for one reason or another so there’s usually 1-2 stalls that need to be cleaned daily. We (barn help) are responsible for filling/cleaning water troughs - only 2 because the main/large herd has a pond - sweeping aisles and making sure barn is clean and tack room is locked up at night.
It takes 1-1.5 hrs/feeding and doing it weekends only covers most of my board.