What evidence shows that Walter is not entirely selfish in wanting to have the in­surance money?

Walter makes it clear that his dreams aren't for himself alone. His dreams are for the family. From the text:

You ain't looked at it and you don't aim to have to speak on that again? You ain't even looked at it and you have decided— (crumpling his papers) Well you tell that to my boy tonight when you put him to sleep on the living-room couch . . . (turning to MAMA and speaking directly to her) Yeah—and tell it to my wife, Mama, tomorrow when she has to go out of here to look after somebody else's kids. And tell it to me, Mama, every time we need a new pair of curtains and I have to watch you go and work in somebody's kitchen. Yeah, you tell me then!