I can speak only to my situation as a retired firefighter and I was indeed a "moonlighter" (November/Downtown).
When I hired on as a firefighter in the mid 1960s after my three years in the army, the salary was adequate for a single man, which I was. I was married two years later and started down that path, a home, children, etc. My wife was a "stay at home mom" raising our children. It was pretty imperative that I bring in extra income to provide for my family. At the fire department I worked 56 hours a week (state law), 24 hours on duty, 48 hours off duty. I worked at anything I could get – construction, gas station, you name it. I put in 28 years of service to my city.
I should mention that Social Security was not deducted from my fire department wages. I did, however, contribute part of my salary to a city pension plan. All of my moonlighting jobs and my army pay were, however, subject to Social Security deduction.
As you can see, If I had relied strictly on my fire department wages, my only income at retirement would be my city pension. Here is the rub – after many years of working those odd jobs, I began to receive notices from Social Security that I had reached enough deductions to qualify for a small amount from them. Great, as my city pension was a fixed amount, no COLA, and after several years of retirement was being eaten at.
At age 62 I went to my local Social Security office to apply for my small benefit, only to be told "You were a firefighter, therefore your benefits will be reduced by 55 percent!” Why? Because there is a little known law, The Windfall Elimination Act, that the federal government passed many years ago to prevent any government employee that doesn't participate in Social Security in their primary job from receiving their fully earned Social Security benefits from any other employment. Gotta love those guys.
I'm writing this because I think “moonlighters” get a bad rap sometimes. I can't really tell you how many hours and days I and the men I worked with at the fire department worked on our own time volunteering at city functions, teaching CPR classes, etc. We were fortunate to be able to do both, work for ourselves and make our city a better place to live in.