I know someone who bought a foreclosed home on the open market (MLS). After they bought it the city inspected it and found the unpermitted finished basement. The city made them pull down every inch of drywall for the electrical to be inspected. The owner tried to reason with them about just taking down certain parts but the city refused. After removing all the drywall the city came back and approved the electrical and said the drywall could be reinstalled. That was 10 years ago and not a single piece of drywall has been put up out of anger over the whole situation.