Most of the people I know doing this are involved heavily in local commerce. Think real estate, insurance, construction, and skilled labor companies (plumbing, A/C repair, landscaping).
You aren't going to pull down 7 figures on a one-man AC repair business. In that type of business, you are just renting out your time, and nobody is paying $1,000/hr for an AC repairman's time. You can scale it, definitely, and have an army of repairmen working under you and then make tons of money, but then you're no longer talking about a one-man business.
I don't think grandparent comment was meant to imply 1 person business. (You are correct in your math assumptions). I just think they mean "small business funded organically or built from the ground up". Besides "1 person" can also mean "1 person and subcontractors" so where do you draw the line at "1 person" anyway?
The only thing I would add though is that many of these businesses were not started by the person running them they were passed to a family member who got something that they could expand upon where the risk had already been taken.
One of the things I have noticed is that 'managing' things is a skill unto itself. And some very successful people I know operate by helping people with skills connect with people who need those skills, and then creating a structure where a fair price is paid for the access.
