For More People in 20's and 30's, Home Is Where the Parents Are
Growing number of 20- and 30-year-olds still live at home with their parents and take longer than their parents did to finish schooling, decide on careers and marry; many seem content with situation and in no hurry to reach previously important milestone's of growth; some social scientists can phenomenon 'transitional adulthood' and say it is partly due to economy in which most jobs that pay enough to support middle-class life require years of advanced education; parents often have mixed views of these arrangements; photos; graph shows estimated median age of first marriage and percentage of grown children living at home by age, sex and race (L)