That question never happens in places with a minimum wage. What you can do is support your employer by showing up early and/or helping out a few extra hours after the shift. Nothing in writing or by force.

As an employer you’d be crazy to do that. Nothing would stop that employee from turning around and demanding back wages.

I've really had a lot of jobs. I would just do anything for a while just to see what it is like. In some places it is as if Hitler won the war, in others the boss or manager becomes a good friend. You don't demand back wages from a friend.

Since that is how the relatively uncontroversial minimum wage law (which has been around since 1938) works, yes, society has generally decided that we do want to tell people, "it is illegal to work for some very low wage." And, while not the parent poster, I agree that it is a useful policy.

That’s a very US centric point of view and appeal to authority. Just because it’s been the law for almost 100 years doesn’t mean it’s the ideal approach.

And several developed countries have no floor other that agreed by through collective bargaining.

https://www.investopedia.com/articles/investing/080515/5-dev...