not for your own property.
In Denver you are required to have a plumbing license and a contractors license. You can be heavily fined if you do not.
Each State in USA have their own standards for plumbing jobs. Most States need the plumbers to hold general license, master license or contractor's license pertaining to that State.
That would depend on which side of the planet your on as some areas have no plumbing codes thus no degree or HS is required
Having a license to install siding is not mandatory. You can install siding on your home with no license. However, if you are hiring a professional to install the siding for you, although having a Contractor's License is not required it is recommended.
Not necessarily, depends what and where plumbing work is to be done. Check with local plumbing authority about needing license or not. Sometimes you need license to pull permits to do plumbing work. Plumbers usually have at least a journeyman's license.
No state license is required, however, general contractors must get permits at the local level. Separate boards license HVAC, and plumbing trades.
Yes you can,but a EPA refrierant certification is required to buy refrigerant and a license in most cities is required for installing equipment.
Yes, because the non licensed people can cause a cross connection with the potable water system
I think you just need insurance or get a contractors license http://www.rld.state.nm.us/CID/faq.htm
license for plumbing what it looks like
New York State does not license "handymen." The state may require a business license if you are conducting a business, and you may need a plumbing license or electrician's license if you will do plumbing or electrical work.
The only plumbing work that you are allowed to perform without a license is for your own property.