Fact is, I can't take a side because I don't know the laws where you're working. Where I live, it is a crime to take money to do tree work unless you are licensed by the city, and you can't get that license without a $300,000 policy. And yes, I did say crime...it's not even a civil infraction...it's a misdemeanor. But, if there are no such laws where you live and work, then there is no unfair competition.
I happen to have a private pesticide applicator's license from the State of Michigan. I got it in order to be able to use regulated herbicides on my own property. I have friends that have asked me to do herbicide applications on their lawns, some of which have offered some money. I always turn those down, because the terms of my license forbid me from doing so for hire. It is unfair competition for me to come in and do that type of work, because I have no insurance policy if something were to go wrong. The guy's that have that policy have to bake it into their rates, so by definition I'm competing unfairly. However, I have done some for good friends for free, simply because the vast majority of lawn services in my area just don't know the first *&^% thing about proper herbicide application, and I don't want to see a good friend's lawn wrecked.
Couple of other points...someone, may even have been you, said that you weren't a business...you were just a person. But here's the thing...once you enter into a contract to perform services for hire, you actually are a business...you are a sole propietor, and the IRS will treat you as such. Now, before someone mentions that we all get paid by our employers, yes...we do, but there is no business contract there. (Even if you're union...that's an employment contract). We're all free to walk away from our jobs on a moment's notice, for any reason or none, so no, we are not all "businesses."
Furthermore, a verbal agreement is a binding contract unless it falls under the statute of frauds, which again varies from state to state. So you are truly acting as a business under the circumstances.
As to who would pay in the event of an accident...depends on state laws again, but there might not be anyone to pay. Where I live, if I hired an unlicensed tree contractor, he would be commiting a crime by working on the tree. If there was an accident, (1) He has no insurance, (2) My policy would probably fight paying because I hired a criminal to do something I shouldn't have. So in the end...maybe my policy would pay, but bet your lungs not for a long, long time.
Now, in your favor, none of that crap above may apply at all where you live. If you don't need a license, and if you aren't required to have insurance, free market rules, baby! Also, my guess is that you know your limitations, and if you think anything could remotely go wrong, you won't take the job.
Both sides have some good points. But I think the tone started out bad, then got worse. Again, too much drama, not enough bullcrappin'!!