I actually work off my board, it's seven days a week, and it's hard work, I feed every morning at 8am sharp, and do stalls, but I don't have to pay for a thing except farrier and vet. The work is hard, but it's really worth it. I make my extra money schooling horses for outside people, doing extra work around the barn, horse sitting, dog sitting babysitting, really anyways I can because if you work at a barn, chances are, it's going to be hard to find a part time job. Though, if you have evening shift/morning shift, you can set your hours at your other job.
Not a lot of barn owners will work with you on board, i'm going to be honest here, few that will work with you on board will be fair about the situation. And maybe those that will wont have the best barn around town, but it's better than not having a horse/barn at all.
Working off my board is the only option for me to have a horse, I just got out of a situation where I was being taken advantage of because I knew more about basic training than the owner of the barn...I was overworked and I didn't get my board/work contract for a month because she kept avoiding it.
You're going to have to find someone who will sit down and work out a contract with you, with what the both of you thinks is fair on it, and give it to you before you move your horse in. If you do find a place, congrats, and i'm glad you're willing to work to have a horse! Just make sure everything is fair, and take things in advance, set up a certain number of hours, and asked to be paid for extra work, calculate your work hours to how much their other boarders pay for board to see if it's fair etc..
At any rate, good luck and sorry for the novel lol!! I hope it works out for you!