Try working as a groom at your barn and pick stalls and bring horses in
I work at my neighbors barn to lag for riding. Or try asking around seeing if they need a sitter of some sort or help of any kind.
Once you're 14 you can work in fast food
Yes I work at my barn to help out with the expenses. So I would try to find something like that first :)
Not sure where you are from but lots of barns in my area have barn jobs in exchange for board or leasing. Try looking into something like this. I used to work so much it payed off my lease each month