I was a working student in Florida, and I had to clean 32 stalls by myself - and sometimes all of the stalls (48 I think there were) by myself. We easily pushed 72-80 hour weeks. I had two weeks to 'get fast' and learn the names of 48 bay and chestnut horses who had little to no markings. It just got to where I physically and mentally could not handle it, and I left.
Eventually I got an internship in Wisconsin. It was an awesome job, with minimal picking. I didn't even have to pick stalls until the second intern got there, and we split the stalls in half, there were 22 stalls. I had to leave because my horse was supposedly going insane at home, but I'd go back in a heartbeat.
Everyone is different, and they'll expect different things. Funny thing about barns is that they want a millionaire job done on a dimes budget, most of the time. In my experience, bartering services is not a good way to go. I hope it works out for you, but I think you really need to express your concern to the BO.
I've got a lovely bunch of Neuticals,
There they are all standing in a row
Big ones, small ones, some as big as your head