We have Horse of Delaware Valley and Equine Marketer locally that are both classified paper publications. The Horse also has articles and Equine Marketer is strictly classified ads.
Most of our dressage and eventing clubs have classified sections.
Hang an ad at the local feed store, tack store and the secretary’s desk at local horse shows.
Depending on what type of job and location you may be able to reach out to the local college with equine studies. They may have students or former students looking and have a means to reach out to them.