Does anyone know what the commission pay is for Solvit plumbing company?

My husband currently works as a plumber and has for almost 10 years. He has an interview coming up and is curious to know what the commission base it. He currently works for only 22$ dollars an hour (which is the lowest hes been payed in years!!) but hes afraid that working commission based will not benefit him. The "base pay" is 400 a week