Gnu-Don't know where you are, but I'd think long and hard about either doing work on a rental unit without the building permit, or doing work that doesn't comply with the fire code.

Your "lad" told you, and it is perfectly true, that they can fine you, and stop you from renting, but he seems not to have mentioned that they can and will compel you to remove the non-complying work, and replace it with work that is up to code--at which point you will be wisest to hire a licensed and bonded contractor, because they will be scrupulously attentive to regulation, and if a contractor's work fails inspection, the contractor has to make it good, and if you fail inspection, you have to make good--