You must be supervised by a high level psychologist if not a licensed PH.D psychologist. A desire to help others, energy, good team worker, willingness to keep learning, adaptive to change, a good sense of humor. State licensure in some areas. If working in a civil service position, you must pass a civil service exam. Yes, state workers union and psychology or counseling associations.
Salary depends on the position.
Able to help others with behavioral or emotional problems. Some people are born with developmental and physical problems for which there are no solutions at the present time. Not that I'm aware of. Exciting and fun - to find ways to solve difficult problems and to interact with interesting individuals. Unpleasant - if physically or verbally attacked by people you are trying to help.