How much money did Jim make a week at his job, and where does Della work? Please give the reference from the story.

Jim and Della do not have all that much money.  That is
partly because Jim is not making as much money at his job as he used to.  You can find
this in the fifth paragraph of the story.  It tells us that Jim used to make $30 per
week but now he is only making $20 each week.  We have no idea why that would
be.

As far as I know, Della did not have a job outside the
home.  There is no reference in the story to her going to work or anything like that. 
The story also says "Twenty dollars a week doesn't go far."  That implies they have no
income but Jim's.