The biggest thing I’m confused about is where the order demand was originating
“ This 3D printing business started with the help of my dog, at the time a puppy, and his desire to see my neighbor’s puppy. We (the humans) began talking, and as we ran through a conversation about dogs, the topic came to his trading card business. He’d source cards all over the internet for his daily WhatNot auctions with thousands of followers. Impressive—not only a home business doing real volume, but a lens into a world I had no idea existed.
I eventually noticed he had a 3D printed card stand, and with a printer at home, I offered to make him one myself. “Great,” he said, “I can sell them.””
So a guy selling playing cards started selling the things you 3D printed?
Is that the business?
Yes, exactly. It was through a neighbor. He had a functioning trading card business to start with, I sold my first order to him, then his clients started asking for prints.
I'd argue that's a "business", there were sales, supplies, a bottom line, et cetera, it's just the front-end part of the business was in collaboration with someone else.
It was pretty random, but there's all sorts of other 3D printing businesses like this for D&D supplies, tool attachments, et cetera.