What episode of keeping up with the kardashians do kendal and kylie start to model?

Kendall and Kylie Jenner start to model in Season 3, Episode 1 of "Keeping Up with the Kardashians," titled "The Beginning of the End." In this episode, Kendall's modeling aspirations are highlighted, and she begins to pursue opportunities in the fashion industry, marking a significant moment in both of their journeys as they step into the modeling world.