Users can be very specific when they look for something.
If you were back in 1860 and looked for a job, your main option was to buy the newspaper, and browse through job ads like this one:
(which, btw, it was a hoax)
In today’s world, users can be as specific as “part-time remote jobs” and get results in seconds.
As a company, you have access to public data such as where in the US people are looking for these type of jobs:
What else they are searching for and how is the competition:
(screen capture from AdWords Keyword Planner)
If you need to recruit expert riders, it will pay off to do a little market research before you launch your job ad.