Along the way I also was able to get free insulation installed (~10k value) using the local utility energy efficiency initiatives as well as laid plastic sheeting in the bare crawl spaces to help with moisture and bring it up to code. 

I like to put a vapor barrier (layer of plastic) and reinforcement into the slab.

The tenant that I am having an issue with is unit 3, the lady in unit 1 just had surgery so I am keeping her can closest to the door to minimize her travel.

If not, I recommend plastic when you do -- they don't soak up smell like wood -- even painted wood.

If you needed surgery, you would not start medical school.

UpdateWe closed on the duplex January 8 (same day that I was set to have emergency eye surgery, but that's another story).

It's not brain surgery, but if you have a thorough understanding of how it all works before you dive in, you're going to be way ahead of the game. 

Rotten plastic dryer vent exhausting into attic.  

If you have fired clay tiles or decent quality plastic it's unlikely jetting will hurt the lines.

The offer was accepted at the end of May but the seller asked if I would delay the close so she can recover from surgery and chemo.