You probably would want to sell your duplex using a creative owner carryback strategy with terms that are attractive to future note investors and to your buyer/borrower.

Wondering how conservative or aggressive I should be on the annual growth rate and income increase with this huge attraction coming in.   

You need to do a cash out refinance if you want to use the leverage its nice to have a property paid for but if your looking to LEVERAGE that means using the equity in one property to purchase more properties you will make more money in the long run but will have a payment on the one sounds like it is producing much income so could be a smart investment stratage.

Tell your friends to go to the local grocery store and ask in the produce department, where they can get lots of free boxes. 

Some people might not even consider an investment if it does not produce 20%+ return vs. some others might be ok with anything above 10%. 

In your case tho using a low down payment second home mortgage will produce a poor rental located 3 hrs from your current home.

The 78745 zip code is an amazing location within 20 minutes of downtown and to all of Austin's main attractions.

The financing terms would negate most of my cash flow and produce an unacceptable ROI..

I think I would default to that model if the house-on-wheels, model didn't produce. 

--Now I want to explain that I'm attracted to this flip because it's easy.