From a purely financial perspective your cheapest money comes from your home.

This was my first purely investment property and there were some hard lessons learned, but despite the challenges, this property has provided me consistent cash flow.

This will be purely for rent and not own occupied as we want to live in Shaker.

We have been able to turn pure rentals 20% down and 0% personal turned rentals into a great strategy that is building a passive income stream for us.

For a more pure IRR calc, you'd need to take the 2008 purchase at $1.75, add another $20k invested to remodel a bathroom in 2013, add another $750k investment in 2016 and then the sale at $3.9M in late 2020. 

What makes it difficult is that it's not purely an investment property - I love the neighborhood and plan on living in the place for some years...Any advice would be welcome!

That's just pure economics.

From a purely cash flow perspective, paying off your primary makes sense, but it's not that simple.I would look at your mortgage's interest rate. 

This is my first property purchased purely as an investment. 

Purely networking.