First, to be literal, a peddler is an itinerant merchant--who doesn't "get a check" (i.e., a salary), but lives by selling merchandise at a price higher than he or she paid for it. An investment capitalist isn't a pedlar, a feudal lord collecting his tithe isn't a peddler, a factory worker isn't a pedlar (tho, as Marx emphasized, she or he is selling/renting labour power by the hour), nor is a store clerk, nor is a prostitute. nor is an actor. Thus we are dealing with a metaphor. That one must do something perceived as socially necessary labour (Marx again) to "get a check" is assuredly true. Thus we all have something in common with peddlers (and prostitutes, hence the commonplace metaphor that we all "peddle our asses."