As the housing bubble burst in overheated property markets around the world, South Africa’s so-called ‘affordable housing market’ appeared to be bucking the trend. From 2010, affordable housing prices were rising and selling quickly, especially in Gauteng, Johannesburg’s city-region, chronically short of actually affordable housing and with a growing black middle class. Touted as ‘SA’s best-kept investment secret’, the affordable housing market offered a lifeline to the property industry and the potential to democratize segregated property markets. Yet, in practice, the tapping of South Africa’s lower-income housing market by capital has been a limited one, narrowly catering to particular subjects and spaces. Drawing on heterodox approaches to ‘actually existing markets’ and qualitative fieldwork conducted in Johannesburg between 2012 and 2013, this paper traces how the boundaries of the affordable housing and mortgage submarket are produced and shift through the investments of multiple communities with their own theories of housing markets and different interests in ‘making the market work’. Despite these investments and contestations, the submarket is narrowly territorialized within developer-driven housing largely in Gauteng for public-sector workers, to optimize the market within mortgage capital’s frameworks of risk, return, race and space. The South African mortgaged affordable housing submarket is not so much in need of market information or constitutive of a new frontier of global finance, as a territorial fix for domestic capital vis-à-vis development imperatives. To investigate struggles over this submarket, I draw together socio-institutional approaches to markets with critical political economy of housing markets and put them into conversation with critical development studies scholarship on markets. This combination allows us to make space for multiple projects of ‘improvement’ and profit in our analyses of market-making, as well as how these are shaped by, and shape, space and conjuncture. I seek to contribute to a growing literature on the geographies of markets from a Global South context where housing is framed as both a market good and constitutional right by examining a case of apparent ‘market failure’.