You're right. It's also true that if I don't wish to expend my labor power in exchange for compensation, I can also buy a factory where I buy materials and labor and sell them for more than they cost.

Can you think of any reason why, when done at scale, these sorts of activities create a class system where not everyone can simply buy a plot of land and build a house, or be an industrial entrepreneur? That there will actually have to be many times as many people who have to sell their labor and pay rent?

Can you think of a way in which the possibility to create profit out of land adds value to that land that is unrealizable to someone who buys it and just lives in it, and is realizable for someone who plans to rent it at market price?