I know none that keep to one person

Then you don't know many small businesses. There are more sole proprietorships than every other type of business combined.

And if there's none, congrats, it's a cooperative!

That's called a "partnership". That's the second most common type of business.

Employment is something workers won in the early 20th century.

Labor laws are what workers won in the early 20th century, not employment. Employment long predated labor laws.

The reason they fought for labor laws is because employment naturally trends toward exploitation, and needs to be reined in through regulation. Unfortunately, influence in labor regulation is now dominated by employer, not employee, so exploitation is not being adequately addressed.

Employer exploitation is not a problem for the self employed.