To get those hours, maybe turn one or two into medium term rentals (you want the average stays to be over 7 days so they don't fall into STR status) which would give her more to do, particularly in the first year of furnishing them and getting everything set up.Alternatively, she maybe she could manage the properties but also get her RE license and try to sell a house or two a year - go to lots of open houses or run them for other agents?

It is the bridge between buying and selling a flipped home.

When you live in that duplex for 2 years and then sell you'll be able to take 50% of the profit tax free (the allocation for the side you lived in). 

I have seen it too many times where an investor will buy an older property or even a new build, they net cashflow similar to you for a year ($100-$200 per month) and then a $5,000 repair or insurance/tax hike here hits them and it's a loss - they either get forced to sell or are majorly setback and unmotivated. 

Then, if it is still negative cash flow, but the equity is there, then consider selling. 

They are more useful IMO for getting chunks of equity right off the bat thru value add and then either realizing that equity by flipping it and using for a down payment on something bigger or hold a couple years and then sell at that point to do that then. 

On the 15th year, the investor and I will discuss together whether we want to sell the house OR continue receiving cash flow.

I don't think the market will continue to appreciate as it has over the past few years and that equity isn't something I can realize until I sell the property which I don't plan to do. 

If you cash flow $1K per month for 36 months, and then sell with the ability to pull back your original investment, would you consider that a win?

With a fideicomiso, the first $200k is tax-free when you sell.2.