In California employees and helpers do not need to be licensed, only the owner of the company. In Iowa and a few other midwestern states the owner doesnt need any kind of a license. Any handyman can advertise and be a plumber, except in the DeMoines area. I live in California and have seen alot of helpers cause alot of damage. I do not like using high pressure water to clear drains. I have seen alot of problems like water hitting the clog and then coming up in another drain in the house! You should always have the homeowner sign a waiver so your not responsible when you screw it up! I do own a plumbing company but I dont believe it’s the homeowners fault if a plumber comes out and says they need the hydro jet and then floods the home and says, oh well, ah, sorry. Use the snakes or do a repipe, thats what we do and knock on wood, we have never had a complaint or secondary damage. If we cant clear it, NO CHARGE.