Prelude to the fall

The following is a section from a Wikipedia article titled Crisis of the Third Century.  I have highlighted in bold certain statements that highlight economic consequences of this breakdown leading up to the final fall of the Roman Empire.  Think of it as an illustration of possible future consequences of an economic crash.

With the onset of the Crisis of the Third Century, however, this vast internal trade network broke down. The widespread civil unrest made it no longer safe for merchants to travel as they once had, and the financial crisis that struck made exchange very difficult with the debased currency. This produced profound changes that, in many ways, would foreshadow the very decentralized economic character of the coming Middle Ages.
Large landowners, no longer able to successfully export their crops over long distances, began producing food for subsistence and local barter. Rather than import manufactured goods from the empire's great urban areas, they began to manufacture many goods locally, often on their own estates, thus beginning the self-sufficient "house economy" that would become commonplace in later centuries, reaching its final form in the Middle Ages' manorialism. The common free people of the Roman cities, meanwhile, began to move out into the countryside in search of food and better protection.
Made desperate by economic necessity, many of these former city dwellers, as well as many small farmers, were forced to give up hard-earned basic civil rights in order to receive protection from large land-holders. In doing so, they became a half-free class of Roman citizen known as coloni. They were tied to the land, and in later Imperial law their status was made hereditary. This provided an early model for serfdom, the origins of medieval feudal society and of the medieval peasantry.
Even the Roman cities themselves began to change in character. The large, open cities of classical antiquity slowly gave way to the smaller, walled cities that were common in the Middle Ages. These changes were not restricted to the third century, but took place slowly over a long period, and were punctuated with many temporary reversals. However, in spite of extensive reforms by later emperors, the Roman trade network was never able to fully recover to what it had been during the Pax Romana (27 B.C.—A.D. 180) of the first century A.D.
While Imperial revenues fell, Imperial expenses rose sharply. More soldiers, greater proportions of cavalry, and the ruinous expense of walling in cities all added to the toll. Goods and services previously paid for by the government were now demanded in addition to monetary taxes. The steady exodus of both rich and poor from the cities and now-unremunerative professions forced Diocletian to use compulsion; most trades were made hereditary, and workers could not legally leave their jobs or travel elsewhere to seek better-paying ones.