I help my friends and neighbors for free anytime they ask me. They return the favor also.
That being said, if I was going to do it for hire, I would NOT give my time away. Also if I was going to do it for hire, and advertise, put up signs, etc, I would make sure I was fully legit, insurance, license, etc. All it takes is one accident, or "unhappy" customer to report you and it all comes to a stop, fines, etc.
I did some bush hogging for realtors for awhile, but it was always last minute type jobs that I really didn't care to do, and it seemed that they always wanted more then they where willing to pay for. Then it was weeks until I would get paid because it was all done through the realtors trying to sell the property. The pay was good, but you can only work so many hours in a day, and I decided that if I wanted to work 12 hour days, I would be better off putting them into my day to day job.
here the township workers report ALL folks they see to the code enforement officer...no permit to work? Expect a visit and the consequences of it.
Several years ago, heck, it may have been 10-15 years ago, several of our local governments started requiring contractors to be licensed with them. So there's several cities, towns, the county, state, etc... that you may have to get licenses/permits with before you can do work inside their boundaries.
You know why that is, right?