As the title says, when you take the Force Sensitive Emergent or Exile specialization when do you gain the force rating of 1? Is it upon unlocking the specialization which means you can dip into it and then immediately jump to the FaD specializations or do you need to spend XP until you unlock the Force Rating talent which increases your force rating by +1? (0 + 1 = 1).
When they take the specialization
From the specialization description:
The Force Sensitive Exile specialization does not have any career skills associated with it. However, when a character purchases this specialization, he automatically receives a Force rating of 1, if he did not already have it. If he already has a Force rating of 1 or higher, it does not increase. - p.276 Edge of the Empire - The Force
The 5th Tier Force Rating Talent would add to whatever the PC's rating would be at the time that they took it (at least 1 as being force sensitive is a per-requisite to taking it).