This paper analyses a model of migrations induced by job mobility within a system of two areas, a rural area where jobs are stable and an urban one where they are unstable. When migration costs are low enough, the agents consider unstable jobs as transitory ones, occupying them only as long as a stable job has not been found. Since stable and unstable jobs are located differently, this form of job mobility induces repeat migration. Moreover, if labour force entrants start unemployed, net migration to the urban area increases at the age of entry into labour force and decreases at later ages. This results conforms to most empirical observations.