Poverty definition has been evolving with developing policies. First to be poor was principally meaning to be out of an easy access to essential resources. After the notion has been enlarged to integrate the fact to be deprive of good conditions for personal fulfilment. Today the state of poverty is assimilated to a state of exclusion, to be "out of development", with a strong link with the "poverty trap" concept. But this conception is contradicted by observation's conclusion about urban organisation of numerous developing countries cities. In these cases, poverty is absolutely not a dropout state but appears has an integrated urban resource. Poverty is a necessary and vital economic element in free-market mechanism of actual urban growth. Using free-market economic growth for eradicating poverty seems an impossible urban target within these developing countries cities. Other developing issue appears during the demonstration. If no regulating policy applied to free-market urban system, it inexorably turns out urban environmental degradations, a drop down of surroundings, quality of life and social living. If poor are the more vulnerable to environmental drop down, the entire urban underworld people are concerned. The economic urban development using free-market mechanism is weakening urban life and environment not only for the poorest surroundings but for the entire urban agglomeration. As eradicating poverty is impossible, perhaps useful urban regulation policies innovations can came out using reducing vulnerability mechanism.