Leading question isn’t it? Chances are if the plumber you use is paid by commission or a fluctuating pay scale they are trained in sales more than plumbing. Don’t get me wrong all plumbers in the state of Texas are required to take continuing education every year. This is yet another awesome reason to live in the great state of Texas. You are required to hold a plumbing license in order to perform residential and commercial plumbing installation and repair.
In order to run a plumbing company you have to have one person on payroll that holds a Master Plumbing License. It is your right as a home owner to ask to see the license of the plumber working at your home. There are three levels of licensing Master, Journeyman & Tradesmen. In best cases you would have a journeyman plumber and a helper or apprentice working at your home. A helper is learning under the supervision of the licensed plumber. If you suspect that plumbing work is being done by a person that is not licensed you can check their first and last name at the Texas State Board of Plumbing Examiners website, the regulatory body for the plumbing industry.
In many cases remodeling companies will contract out the plumbing work to a licensed plumber, if they do not have one on staff. In some cases they try to do the work themselves. This sometimes can cause more harm due to the fact that when something malfunctions or breaks a licensed plumber will have to be called to fix the problem. This can end up costing more and taking longer for the project than if it would have been done right the first time with a licensed plumber. I wrote about this a while back of past customer examples here https://theplumbersbride.com/2012/03/16/tile-shower/
There are also some high schools that offer a work study program called a co-op where they can work in a trade for the last 1 or 2 hours of their school day. Bear actually did this back in 1990, and learned from the very best. Our plumbers and apprentices are paid by the hour, not commission. Bear has high standards and even higher expectations for his guys.