What made Tom visit the Ewell's house in the first place?

Mayella says that she called Tom Robinson inside the fence that evening and offered him a nickel to break up a dresser for her.

Tom walks by the Ewell house to get to work. Mayella often sees him (she kind of ways for him) and asks him to do odd jobs (really she was just lonely). Tom obliges because he feels sorry for her plight. In this instance, Mayella wanted more than company.