They often survived by calling in political favors. Because of marriage alliances many nobles had relatives throughout Europe. If they were forced into exile they relied on these alliances, which were essentially political, for aid. If those failed them, they prayed that their old friends would offer them some help.

However, they did not labor, which was seen as beneath their class. They would go live in exile with a fellow noble family and pretty much survive off of that person's generosity. Most of the time the banished party would endlessly plot their return or try to infiltrate their way into the local court, but they wouldn't pick up a day job and start herding cattle.

The English Wars of the Roses give us some excellent examples of how this worked since it was a time when nobles were continually cycling in and out of power. Queen Margaret of Anjou and her young son were ousted from power following the Battle of Towton in 1461 and forced to flee to France. For the next nine years she lived at the court of her cousin, King Louis XI of France. As an exiled queen, Margaret lived off of Louis's generosity. He allowed her to live on his lands, payed for her housing, and gave her a small stipend for spending money. A few years later, one of the wealthiest men in England, Richard Neville, Earl of Warwick, or the Kingmaker, is also forced to flee. Together with Louis XI and Margaret, three people that hate each other plot to recapture the throne of England. They do so briefly in 1470, which causes King Edward IV to flee to the Duchy of Burgundy, where his sister is married to the duke, Charles the Bold. As an exiled king he has absolutely no money and so he survives by a small stipend given to him by Charles and goes around begging rich Frenchmen to help him regain his crown. Eventually Charles agrees to help him and they retake the English throne, sending Margaret of Anjou back into exile where she becomes a ruined pauper of a noblewoman. Her cousin Louis has to role his eyes and put her up even though she now has absolutely no claim to power because it's the "chivalrous" thing to do.