In Cantillon's system, the primary division in the population is between landowners and the rest. Landowners either cul tivate their land directly, pay the costs, and enjoy the surplus of output over cost, or they let the land to farmers, and enjoy the rents. Rent income is simply the surplus of output over the incomes of farmers and farm labourers. The prices of all non-agricultural goods adjust to cover the costs of producing them. All non-rent incomes, in this framework, are part of costs, so Cantillon said that non-landowners all lived 'at the expense' of the landlords. His discussions of incomes are mainly taken up with discussions of the incomes of non landowners; once they are determined, landlords get what is left over.