Answer:
Yes?
Step-by-step explanation:
I don't really know what the question is here but I can say it is legal with exceptions. There is nothing that can get either party sent to jail. There is a downside. Let's say Brian decides that the project is too hard for him and he gives up but Liz has already made 14 dinners and she wants her plumbing fixed. She can't really sue Brian because there were no contracts and no written agreements. It's a case of "He said, she said." In reality, these kinds of deals happen all of the time and it's no big deal.
When money is thrown in, things tend to get more complicated. When someone pays for something, the money changes hands. If the worker doesn't record the payment in his taxes, then it becomes tax evasion and that's real bad.
I don't really know what's happening here but I hope it helps!