That said, if you'd like knowing your place is 100% paid off then tackle the mortgage.

I've been listening to Brandon and Josh at 1.5-2x speed commuting 4-5 hours a week (lol, it's true, people think I'm nuts when they hear me) and tackling a little bit of reading (as much as I can with a 20 month old and a 2 week old at home.)  

Knowing just 20% can help you tackle 80% or more of the issues that will ever come up.

I feel like I'm ready to tackle my next adventure.

You’ve tackled the loan issue, in large part through good advice in the thread that helped you know what questions to ask.

I'll let someone else tackle the duplex vs. single question.  

I justified this because I could tackle this down payment on my own (no investors) and I wasn't relying on the cash-flow to get into the deal.

Long story short, i refinanced, i was able to move back into my home and now i am in a much better place with a little bit more knowledge than before and ready to tackle this thing called REI!

I'm waiting to hear back from some contractors on a few different ways to tackle it.

The plan was to tackle a complete renovation of one of the 4 units first.