why does Gatsby offer Nick work? how does Nick feel about this?

In Chapter Five of F. Scott Fitzgerald's The Great Gatsby, Gatsby make plans with Nick for him to orchestrate the meeting between Daisy and himself. As they talk on the lawn, Gatsby offers Nick a job after Nick has already been approached in Chapter Four by Meyer Wolfscheim, who has said to Nick, "I understand you're looking for a business gonnegtion." So, when Gatsby rather indelicately asks Nick,

"Why, I thought--why, look here, old sport, you don't make much money, do you?"

Gatsby then offers Nick a job as a "confidence sort of thing." This offer has two implications attached to it. First, with the previous encounter with Meyer Wolfscheim in Chapter Four, and now with the rather nebulous offer of a job in "confidence," the mid-Western Nick is insulted by the suggestion of illegal activity. Added to this, Nick feels insulted by the offer made "tactlessly for a service to be rendered." So, as a matter of pride, Nick "cut[s] him off."