You've hit the nail on the head, except it won't be at the beginning. It will be a few years later.
With almost all partnerships where one man is just the money man, the worker will seek ways to buy him out within five years. You always want 100% ownership and control.
I spoke with UL several years ago. At that time, it wasn't very much to go to their school and become certified. After that, I think someone comes out to check your shop. Then you'll have a certified UL508A shop, and put UL certification stickers on the panels yourself.
Keep your 100% ownership, and get a loan. It will be under $10K total.
If he's a good salesman, then hire him as a salesman. Give him a commission. He doesn't get to be part owner unless he's going to get his hands dirty. Otherwise, you will quickly become "his employee" as he starts calling the shots in order to protect his investment. Then, you will be looking for a way out.
Watch Shark Tank.