Gatsby does not actually offer Nick employment but suggests that he could help him out financially through his vast network of business connections. Nick resents and declines this offer of assistance because he knows Gatsby is only offering to reward him for enabling him to meet with Daisy and for them to use Nick’s little cottage as a  place for further meetings. Nick does not want to feel he is involved in something immoral and reprehensible. He has a very high sense of propriety and rectitude. Gatsby, on the other hand, is used to getting involved in all sorts of shady dealings and thinks nothing of offering, in effect, to pay Nick for services rendered. Throughout the novel, Nick’s involvement is subject to criticism, and he is sensitive about it, as is his creator F. Scott Fitzgerald. Because of the choice of narrative method (minor character point of view) Nick not only knows about Daisy’s adulterous relationship with Gatsby, but he actually knows a great deal about Tom’s adulterous relationship with Myrtle Wilson. One of the reasons that Nick decides to move back to the Midwest is that he has come to feel tainted by the mores of the eastern United States.