Final answer:
The line from the narrative marks the end of the shepherd's former way of life and signifies his desperation and longing to reclaim his livelihood as he transitions into poverty.
Step-by-step explanation:
The line "I need money to buy some sheep" marks a poignant moment in the narrative because it encapsulates the tension between personal dreams and the harsh realities of necessity that the shepherd faces.
The shepherd, previously depicted as prosperous and content with his flock, faces a devastating decline into poverty. With his flock dwindled, the line about needing money transitions from a pastoral dream to a dire necessity; the shepherd requires funds to regain his livelihood and identity, which are both bound up in his sheep.
The ending of Part One with such a line is significant: it symbolizes the end of a certain way of life, represents the shepherd's desperation, and embodies a broader theme that is central to the literary work.