Home addition doesn’t show on tax records

[Sam U.]

Looking at a house in a great neighborhood. Most houses sell quickly and for well over asking price in the neighborhood. The agent told me that the home addition doesn’t show up on tax records and that is why the house has been sitting.

Does that mean the addition was built without permits? How will that create issues if I were to buy it?

Is this a diamond in the rough or do I run from the potential issues? It’s in almost “move in” shape and has a large upside with developments in the area