Eighteenth-century architect-builders were a small group, but important for understanding the market strategies of knowledge-based experts in an age of rapid growth in technical information before the creation of modern professions. This article confronts a teleological historiography of emerging professionalization. It is focused on Robert Mylne and several of his contemporaries in Edinburgh and London, including a number of successful London-based Scots who were active as architects, builders, engineers, and surveyors, and self-styled in all these areas when it suited them. It supplies an account of what it took for building experts to establish themselves and flourish in big cities and the ways in which such experts navigated, controlled, and accommodated an environment of unregulated expertise that largely suited contemporary practitioners. Individual, family, and collective market strategies are examined in detail and the final section is a close analysis of the activities of the Architects Club in the 1790s.