Personally, I don't see any reason why the spouse should have any
problems during N400 process, if the primary applicant quit the job
right after getting GC.
It does seem logical to me as the individual is a Permenant Residient and
has no bearing on the primary applicant once he/she gets GC. This can be
backed up by the fact that the spouse retains his/her GC even after getting
divorce from the primary applicent even in those cases where the GC is
based on marriage.
In fact, I haven't read in any forum - at least in this forum - that a person was denied his/her N400 just because he/she quit the job right after getting the GC.
Good luck
howdy_howdy
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