Why does Charley visit? How does he feel about Willy? How and Why do they insult each other?

Charley and Willy are neighbors and are in contrast to one another. Charley is a successful businessman and has a successful lawyer son. Charley helps Willy with his debts and even offers Willy a job. While Charley seems to have all the answers, Willy still feels put down, yet he mourns the fact that he thinks Charley is his only friend. They insult one another because Willy sees Charley as somewhat "girly" and he also seems insulted by the job offer.