What is the significance of Willy being a salesman in Death of a Salesman?

There are several ways in which this is symbolic and significant:  First, a salesman is a person who puts him or herself out to the mercy of his or her own talent to convince people to buy what they offer. This means, that a salesman should be a powerful, enthralling, convincing, magnetic, and enforcing. This, Willie Loman was...once.

Willie, having lost all these qualities gives the reader the exact picture of who Willie is now, and gives us an schema of what his intellectual power is at this point.

Another significance is that a salesman is also a person who cannot be thought of as a solid foundation to support a home. A salesman is way too dependent on circumstances, making him a very vulnerable and, in the end, breakable person. So was Willie. His life became a consequence of his decisions, and of the choices he made in moments of weakness and this is why, in the end, he only had memories to live by, and lots of things to feel sorry for.