There is a girl here (She's 12) that earns almost all of her show money herself, even when she went to pony finals...and she's not even old enough to have a "real" job. She also just bought herself a new pony while at finals..with money she earned herself (I don't me a schlump pony, it's a welsh that can jump over pretty much ANYTHING) What she does is...
Cleans tack for people...both at our stable and sometimes if there is a big horse show at the fairgrounds she will set up a booth and clean tack there (it costs money but she usually makes way more than she paid for the booth).
Show grooms... she will help get horses ready for show (her parents will only allow her to actually bathe a horse the trainer says is safe for her to bathe fyi). She does the show braids, etc....which takes a while but she gets paid major dough for that one. I f you know how to do a decent show braid, that can help.
She cleans/organizes peoples tack sheds. It's so cute, she even leaves horse mints lol.
She also does he baby sitting, pet sitting etc. But she also offers herself out as a "mom's helper" which is different than babysitting. She helps do some of the chores around the house...single mom's LOVE this as it's really hard when you have children under 3 to even do simple things like clean tubs, wash dishes, make a decent dinner.