The trades that were still somewhat prosperous, such as those connected with building, were productive of hardly any benefit for the commonwealth, because here too the system of employing slaves in every more considerable undertaking intervened: in the construction of the Marcian aqueduct, for instance, the government concluded contracts for building and materials simultaneously with 3000 master-tradesmen, each of whom then performed the work contracted for with his band of slaves.
Money-Dealing and Commerce The most brilliant, or rather the only brilliant, side of Roman private economics was money-dealing and commerce.

First of all stood the leasing of the domains and of the taxes, through which a large, perhaps the larger, part of the income of the Roman state flowed into the pockets of the Roman capitalists.

The money- dealings, moreover, throughout the range of the Roman state were monopolized by the Romans; every penny circulated in Gaul, it is said in a writing issued soon after the end of this period, passes through the books of the Roman merchants, and so it was doubtless everywhere.

The co-operation of rude economic conditions and of the unscrupulous employment of Rome's political ascendency for the benefit of the private interests of every wealthy Roman rendered a usurious system of interest universal, as is shown for example by the treatment of the war-tax imposed by Sulla on the province of Asia in 670, which the Roman capitalists advanced; it swelled with paid and unpaid interest within fourteen years to sixfold its original amount.

The communities had to sell their public buildings, their works of art and jewels, parents had to sell their grown-up children, in order to meet the claims of the Roman creditor: it was no rare occurrence for the debtor to be not merely subjected to moral torture, but directly placed upon the rack.