I've been considering adding more space to my duplex. My dilemma is that if I pull any permits, my property taxes will go through the roof. If someone is holding a property, and plans on doing work up to code why would you ever pull permits? It just seems you are opening yourself up to the city charging you more money in fees, taxes...
Mostly because that's the law. If you do unpermitted work you could get a code violation that could eventually become a lien, a stop work order, depending on the municipality they could make you tear off the extra square footage you add. IF you get caught. You may never get caught until you try to resell it, and it could become problem then if the new buyer has a lender.
Every municipality is different. Here in our area Hillsborough is a little more lax than Pinellas.
I dealt with a fix and flip where the rehabber was caught doing unpermitted work and ended up giving us the property deed in lieu. The inspectors made us open up walls and trench the finished basement to expose plumbing and electrical. They only required a few minor changes, but the damage and repairs were extensive. Some of what they made us trench was done decades prior.