Defoe: he spoke out against people who "barter baubles for the souls of men" and yet he invested heavily in the slave trade and maintained that it was "the most useful and most profitable trade . . . of any part of the general commerce of the nation."
Even though Defoe felt this way personally, I think that it is portrayed in the story that RC did not have to have people around him to be successful. He not only was able to train people in how to care for the island and to survive, life seems to come and to to him. He had the desire to keep on moving towards success. I believe that him "owning" another person was not what he wanted, but that he desired a friend. He knew he could be successful with Friday.