How can i collect cash from a side job, i was helping him as a mover and he owes me $400?

I helped him a few times and he paid me for the first week about $400 and then i helped hime a few days later and he never paid me and now he won't answer my calls. I know there a tax issue but i havent cleared $600 yet so i dont think it has to be filed but i would like to get the $400 he owes me for the work and hours i put in. Any Ideas on how to collect. He lives in the same town as me within a mile but just not sure where. by the way we live in a chicago suburb small town