What effect does Homer have on the story?
Homer creates the conflict around which Faulkner's tale revolves. Without Homer, there would be no story. Emily's life would have probably plodded on unchanged until her own death and the townspeople would never have been enlightened about their selfishness or negligence.
Techinically, Homer provides both the rising action and the climax. His advent into Emily's life propels change, causes her to go off the deep end, and eventually kills him. Homer is even the impetus of the falling action, as it is his corpse that causes the townspeople to understand the (probably) preventable tragedy.
Homer Barron highlights Miss Emily's decline. He does this in several ways. First of all, he is her first and only beau making it evident that Miss Emily struggled in the relationship department. Also, Homer was not the type of man a good Southern belle should be courting, yet she goes out with him anyway demonstrating that she is either desperate or not the Southern belle she was raised to be. And finally, the death and grotesque display of Homer in Miss Emily's home reveals her depravity and possible insanity.