For me, as a barn owner, a lot would depend on your actual knowledge. I have a boarder and occasionally allow her to work a little of her board off but it isn't a lot because she's very inexperienced. She can pick, she can fill waterers, she can place feed in the appropriate feeders and lead most of the horses in. But it's all under supervision. I wouldn't leave the place and expect her to cope, she couldn't handle an emergency.
So......someone who could, feed 2X/day, handle all of the horses including the stallion, do the picking, cope at least well enough to stop bleeding in a minor emergency or had enough knowledge to recognize a major vet emergency and get the vet headed out to the ranch and was capable enough to at least keep things calm til I got back or the vet got there, THAT person would be worth a LOT more to me.
How much do you know, how many horses do the barns you're looking at have? How good of a manure picker are you? I can pick 10 stalls in less than 1 hour unless someone got REALLY messy. My boarder takes 1 hr to do one stall kinda sos so.
Are you comfortable around stallions? Broodmares in heat? Broodies about to foal? Can you help with foal watch? Can you handle a broodie with a foal at side? Handle the foal? Can you handle deworming a horse on your own? Having a list of your actual horsemanship type skills will be handy for you.