Rat wall for a shed?

[James De Silva]

Hi all, I could use some advice. I have a property which has a shed in average to poor condition. The City of Westland has received complaints of rats near the shed and asked me to build a rat wall around it. Also, it's seems the shed was originally built without a permit. How much would it cost to build the rat wall and to get the necessary permits. (it's an good sized shed). Should I just demo the shed instead and if so, do I have to compensate the existing tenants. I don't think they use the shed at the moment.