For the same level of qualification, the standard of living of young people who no longer live with their parents is lower on average, but also less dispersed, than that of young people who still live with their parents. However, those who have moved away from their families have much higher earned income since their labour market situation is far more favourable, and do not report financial difficulties more often. Several factors may explain these characteristics of those who have moved out and of co-residents. Young people still living with their parents can benefit from their parents' income and from economies of scale. This choice is more common among the less qualified, whose employment situation is the most difficult: it does not prevent them from having high poverty rates or being in households that often feel that their financial situation is difficult. Conversely, young people from more privileged backgrounds or who are better integrated in the labour market are better equipped to deal with the drop in standard of living associated with autonomy. This is all the more so as they continue to benefit from intra-familial transfers that are not accounted for in the standard of living indicators. This is particularly true of young people who have moved away and are in initial training, more than half of whom are helped by their relatives. Undoubling appears so to be highly selective and this selectivity must be taken into account when the standard of living of young people and its determinants are studied. To do so, a joint model is used: standard of living in the event of undoubling, and the choice of living away from the parents. It confirms the selection effect: a lack of qualifications and difficulties on the labour market are obstacles to undoubling. Additionally, once the selection effect is taken into account, young people who still live with their parents would have a lower standard of living than the others if they moved away, based on identical pes