I've always suspected that the 'work' verse was Ewan MacColl adding to the too short version he had, [as people quoted above have added verses] since the rest of the song is not about 'settled' employment. In Alan Lomax's interviews with Jimmy MacBeath, Jimmy talks about spells of employment on farms etc, but Jimmy was of 'settled' stock. Can't think of Scottish travellers talking about being ploughmen or bridgebuilders.