These roofs are 3/4 inch thick , 6in wide planks .

Of course, my actual bid on the property could vary widely once I see the property as well. 

Any advise on how to play the angle?

I speak to other investors in my state (NJ) and they all agree that its a state wide issue.

Since I see that you are in the area, how is the market wide there?

The units will be 20 wide by 30 deep with no garages (600 sq ft a floor). 

I’m a week or two out from starting demo and site prep for a brand new double wide.

Maybe have a discussion that you are afraid she can't afford the rent, and you are considering giving her notice because of this (this nips off the "I'm a bit short" excuses)  along what would be necessary for you to be comfortable allowing her to remain as a tenant (catch up on the behind rent, maybe over 3 months period  AND all occupants PASS background check) . 2-3 working adults SHOULD be able to come up with the rent -- I don't imagine that you are gouging anyone.It is possible that if there is a wide open door in front (no 30 notice required if you move in the next 45 days!)

Honestly i have no clue which angle he was ultimately trying to go at, but it sounded like he works with a lot of investors who own real estate that produce more deductions than they have in income to claim on taxes, the point he kept repeating was that you can calculate how much income on a property could maximize the usage of all your deductions, then either pay down to this point and maintain it, or refinance the property in a shorter mortgage to gain income and bring the level back up to this level every so many year or after paying it off. 

The field is wide open.