Employers make their living by selling the goods and services which are made by the wage-slaves whom they employ. Members of the landlord class make their living from renting and selling real property which they own.
To sum up: the employing class makes its living from selling the property which its wage-slaves produce. The landlord class makes its living from renting and selling the real property which it owns. The working class makes its living from selling its skills and time to the employing class for a wage. Only the working class owns a property which can add wealth to what wealth already exists in class dominated society. The workers are forced to sell their skills and time to the employing class because they don't own any other exchangeable property other than maybe the house they live in, if the bank doesn't own it, or their socks and shoes. The employing class owns the places and machinery needed for the production of wealth. The employing class could be nested in the State apparatus or, more likely in privately owned corporations or small businesses. It is because the working class is obliged to sell their life-time to another class that they are wage-slaves. They are in bondage to their employers during the time they've sold themselves for.