That is a practical decision to make after the immigration options are reviewed. A spouse may have a dependent route without a work route, so permission to accompany the TN worker does not resolve the second-income timetable. Keep those milestones separate.
Set a household decision date
Agree on the latest date by which the family needs reliable information to avoid housing, school, or employment commitments it cannot reverse. Ask whether the principal employer can accommodate a later start or a staged family move. Record what happens if the spouse’s application takes longer or is unsuccessful.
No general TN processing estimate can promise when an independently authorized second salary will become available. Set a household decision date and a review interval, because the situation will not hold still while the family waits. Agree the latest date by which reliable information is needed to avoid housing, school or employment commitments that cannot be reversed, and agree what happens if that date passes without an answer.
Ask whether the principal employer can accommodate a later start or a staged family move, and obtain the answer in writing while goodwill is high rather than after a delay. Record what follows if the spouse application takes longer or is unsuccessful. No general processing estimate can promise when an independently authorized second salary becomes available.