Willy's life was about making money. As a salesman, that is all he strove to accomplish. Indeed, it was his job. In the end, by killing himself for the insurance money, he was still doing the same thing: striving to make money. His whole life he seemed to be going about things in the wrong way and he applied this same level of ineptitude in killing himself. Willy and Linda had only one payment left on their house, the fridge, and numerous other things, and then they would be in the "free and clear." Yet this is when Willy Loman decides to succeed at killing himself before those things could be realized by him and his wife as a couple.
Willy leaves in his family a legacy of failure. Maybe not for Biff, but for Happy. It is easy to see who more closely resembles Willy in temperament and characteristics. Biff resembles Willy's older brother Ben in a way, while Happy has the same younger sibling syndrome that Willy had when he was growing up. Admittedly though, Willy sort of bred it in his son, and it could be considered a cycle because that was probably how Willy's father treated him. The only difference in the two situations is that Willy didn't leave his children entirely, although he was on the road a lot and not able to be with them as much as another man with a different job would be able to. Ben was treated as the golden child in Willy's family and he passed that same treatment to his eldest son Biff, possibly because it's the only behavior he knows. Perhaps saying that Willy left his family a legacy of failure is harsh. But it is true that he has left them with the same unreachable ideals and dreams he held. The very same ones that led to his demise. In essence, this is the same as setting them up to fail.
The apple does not fall far from the tree, but let us hope that Biff and Happy are not as willing to sacrifice their very lives for the sake of money.