The shacks in the shantytowns of Lima, Peru, to tin-roofed mud huts in the slums of Gujarat, India, insecurity of tenure and uneven income streams force the poor to build their homes tentatively, one wall at a time. Yet the poor lack access to financial institutions and financial products tailored to the way they build. This, despite the fact that in so many developing cities around the world a majority of the population lives in slums - 60 percent of Nairobi’s population, 82 percent of Lima’s population and that most housing is built informally and progressively.