Permit (unpermitted triggers for Bldg Dept)

[eigoya]

Looking at a home which has at least two unpermitted baths and a couple of rooms. If we buy and want to build a permitted addition, would it trigger a reexamination of house (ie: we would need to get additions permitted or removed?). Any input appreciated (and yes, we could just build unpermitted but I’m looking at what the cost (emotional, psychic  and financial) for having to do this…