I’ve worked at and boarded a few barns, and can tell you its highly variable based on just how the barn operates.
Barn 1: 45-55 horses, all have stalls. 1 Full time on-site worker. He feeds (no feed prep, just a cart with all the feed/supliments) hays, and then starts turnout. 2 more workers join at 8:30-9am to help with turnout. Some of the feilds are quite far. They all 3 dump water, bring hay bales in, drag rings, muck (using a large cart down the aisle, then dumping in spreader outside) add shavings, etc. Extras depend on the day, but holding for vet/farrier, cleaning, laundry. They take blankets/boots on and off. Horses come in at 4 or 5pm, fed, hayed, spot mucked.
I can say that barn was EXCELLENT. Lots of work, as horses are, but everything got done without workers rushing around, hurting themselves. Barn was spotless and perfect. Workers payed attention to horses health. No one batted an eye if they napped on the hay or chilled with the boarders since they had the time to do a good job. Everyone was paid hourly except the live on site worker. He’d check on the horses at night and lived in an apartment anove the indoor ring and had a window he could see the whole barn from.
Barn 2: around 35 horses. 2 full time (8am to 4:30pm) workers + part time mucker. Not all the horses had stalls, but ALL horses HAD to come in to eat/be available to be ridden. Everything was always rushed. Not enough feild space to accomidate all horses, so there were FOUR daily turn in/turn out sessions with blankets taken on/off or swapped for lighter/thicker each and every time. We fed round 1 horses, blanket, turnout/turn in (having to juggle up to 6 horses cross tied in order to even do the swap since all fields and stalls were full) feed round 2, un-blanket, hay, dump water, prep food, turn in/out round 2, hay, blanket, barn chores, turn/in out round 3, hay, blanket, exactly 30 minute lunch break (luckily, food provided) get hay from hay barn, afternoon feed round 1, blanket, turn in/out round 4, blanket, afternoon feed round 2, hay, refill water, clean. It was an absolutley horrible schedule. There was no room for breaks and for taking it safely and slowly. If someone came to ride a horse, the whole schedule is up-ended and a massive re-filing of horses must be undertaken. Workers were paid hourly at $10 which is highly not good enough even for a relaxed stable hand job in a low cost of living area.
I’ve been at many barns inbetween, but I just want to emphasize that number of workers doesn’t necissarily line up with number of horses. Its all about the organization! Its faster to muck empty stalls than full ones. Its faster if you can unload hay from a tractor. One thing you could try is 1 full time worker all day for feeding, mucking, barn chores, and give a boarder or 2 a cut off board to help with turn in/out morning and afternoon, water and hay.