Yes @Patrick Philip, you can have your handyman build you a new house if you want and nothing is going to happen if you do not get caught and your workers do a good job.
Lots of handy man do a great job. Some have more knowledge and experience than a few contractors. License contractors with liability insurance cover you, in case you have an issue, you could have their insurance pay for the damage without using your policy.
But the issue is not just to have the work done by a licensed contractor. The city officials and the Building Code was created to ensure safety. They want you to get an inspection on the work and verify that was done according to the current Building Code.
You can manage your handy man and call for inspections on your personal property without the help of a contractor. But inspector will want to see what it was done.
Take a look at your insurance policy and talk to your broker to see what it is covered and if they will cover for work done by you or your handyman in case a tenant/someone try to sue.
Again you can do anything you want. I am not going to tell you what you should or should not do with or without a permit. That is your decision at your own risk.
Your billionaire real estate investor/mining magnate friend, not even worth mentioned.