We’ll be adding three new jobs: dark knight, astrologian, and machinist, and they’ll start from level 30. The job quests for each of these three new jobs will be located in Ishgard. If you want to start leveling these jobs as soon as you enter Ishgard, you’ll be able to do so without progressing through the new main scenario story. You’ll have to be at least level 50 for the new main scenario. By accepting the first job quest, you’ll be able to level up along with the story.
I took this as meaning that the first job quest for the new jobs are at lvl50/lvl51 and above