Let's follow that line of thought.
So we're in a socialistic society. There are no emploeyers and employees, everyone is free to enjoy the fruits of one's labour.
One particular labourer however is very very good at doing something, he came up with a whole new method or something along those lines. He decides that with some help he could achieve something really great, so he decides to offer money for some people to work under his supervison using his enhanced techniques. Some people refuse his offer, since they figured theye were better off working for themselves. But others decide that they can more money that way, so they accept.
The above scenario can only lead to 2 consequences:
a)You prohibit people from working for that guy, in which case you are not a free society at all.
b)You end up with employer and employees, bourgeouis and proletarians. Capitalism.