When you start dealing with people with unpredictable lifestyles and with income that might be variable month by month, you can't just use the same computerised systems of default and interest that you use for people in regular salaried employment. Muhammad Yunus's microfinance model, which operated in parts of the world where everyone's lifestyle was precarious, had shown that. You had to know exactly who you were lending to, and establish more intimate and flexible models based on that knowledge.