The information we ask for has always been sufficient for us and we've not had pushback.

Understand your approach, but at the end of the day (assuming we're discussing analysis in support of a BUY vs WALK decision), in my opinion, IRR(Internal Rate of Return) is too academic and the NPV(Net Present Value) has factors one can adjust.We see lots of newbies just learning to calc cash/cash & cap rates and these are sufficient to make the go/no decision, using the K.I.S.S principle.Attempting to add IRR & NPV to the learning curve is not a requirement - - for you, it's another confirmation you're on the right track.

Although you're going to owner occupy, I suggest basing your valuation under the assumption that you're not - you want the duplex to be self sufficient.

Is 500 yellow letters to absentee owners sufficient?

If you have an emergency repair and lack sufficient funds in your SD account you may find yourself between a rock and a hard place.

I'm hoping a CPA or tax lawyer can tell me what the IRS has considered 'sufficient' in the past or if the basis is ever called into question?  

If you're going to wholesale, you need to have a knowledgeable real estate agent on your team or access to sufficient data to run your own comps.

You could even (potentially) show it with the existing tenant in place, if you give the tenant sufficient notice (check local laws) and you trust the place isn't a pig-sty.Good luck.

Quality over quantity in this case.2.

You don't need a reason to do this, you just simply need to give them sufficient notice as required by your state.