Can anybody be a construction guy, regulations?

Do not hire anyone to work in your home on plumbing that is not a licensed plumber. Hire only a licensed and bonded plumber to do plumbing work in your home. This way you are not at risk if he or one of his workers is injured on your premises. A licensed plumber will have his license # printed plainly on his truck. Whether he pays taxes or not is not your responsibility. Pay him with a check and ask for a receipt. Know upfront what the cost estimate for the job will be and get it in writing. If he refuses, hire another plumber. Call your local chamber of commerce or the better business bureau to ask for a recommendation of a good trusted licensed plumber. You could also ask friends and neighbors to recommend a licensed plumber. Do not hire anyone to do plumbing work that is not licensed in your state. Ask to see his license if you have any doubt. Do it this way and you are protected and will get the job done right the first time. It may cost you more to go with a professional but I highly recommend you hire a pro who is recommended by friends, family, or the BBB and not someone who is not a licensed plumber by trade.