Short of cash and unsettled in their careers, young Americans are waiting longer than ever to buy their first homes.

The typical first-timer now rents for six years before buying a home, up from 2.6 years in the early 1970s, according to a new analysis by the real estate data firm Zillow. The median first-time buyer is age 33—in the upper range of the millennial generation, which roughly spans ages 18 to 34. A generation ago, the median first-timer was about three years younger.