I doubt a contract spelling out expectations and such was involved. Probably just a verbal you do this job and I pay you this much. Given the hire-an-illegal route taken, this is probably not a bad assumption.
Without said contract, it's going to be hard to claim against the shoddy work (granted it would be equally hard for him to claim compensation). But do you want to deal with a crazy immigrant that is mad at you and can act with impunity (what are they going to do - deport him? hahahahaha)?