Thank you for your comment, this is what I had wondered about, perhaps the previous homeowners doing something wrong. My dad had a commercial property where his tenants added a bathroom. He tried to do something with the building later, and the city noticed the bathroom wasn’t on the original plans. He got hit with an almost $4k fine for not pulling a permit, even though he didn’t know they had put in the bathroom at the time. That’s more along the lines of what I was worried about, because I haven’t done anything to the house myself.