Radio broadcasting falls under many disciplines.
If you mean strictly on air talent then take some college or university courses as a starting point. However, it often isn't a course that seals the deal, rather the voice and style that captivates the managements interest.
There are technical side too. Maintenance, antenna and transmission, service and procurement of parts and equipment to name a few based on wattage and signal strength.
Other departments include advertisement, sales, producers, editorial, script writers, researcher, record librarian and others.
Salary is based on experience and market demand.
I worked in broadcasting briefly before joining a daily newspaper years ago. One piece of wisdom I can offer is this:- Staff turnover is at the whim of not only the management, but also the owners. It is a time sensitive occupation. If your audience is a youthful demographic, they don't want on air talent over the age of 30. Likewise, if your broadcast signal is predominately a mature audience, management whats an intelligent, a mature atitude and an ability for talk at their level.