Career
Eric was determined for and started a career as cleric. However, after his two elder brothers John III and Albert V had died without heirs, Eric III quit the clergy. Eric consented, when on 14 April 1359 Albert V, short in money, sold the Herrschaft of Mölln to the city of Lübeck in return for 9737.50 Lübeck marks.
The parties agreed upon a repurchase, however, only by the duke or his heirs for themselves, but not as a middleperson for someone else. In 1370 Eric III succeeded Albert V as Duke of Saxe-Bergedorf-Mölln, a highly indebted branch duchy of Saxe-Lauenburg. So he pawned - in return for 16,262.5 Lübeck marks - all the remaining unencumbered parts of his branch duchy, to wit the Herrschaft of Bergedorf, the Vierlande, his half of the Saxon Wood and Geesthacht, to Lübeck.
Eric III only refrained a life tenancy. Lübeck and Eric III further stipulated, that once he would have died, Lübeck will be entitled to take possession of the pawns until his heirs would repay the cr and simultaneously exercise the repurchase of Mölln, altogether amounting to the then enormous sum of 26,000 Lübeck Marks. Under Eric IV the two branch duchies merged again into a reunited Saxe-Lauenburg.