So if you expect that to continue, on a combined property value of $925k that would be $51k per year in appreciation gains, for an overall return of (0+51)/500 = 10.2% per year.That's not a bad return, but it is 100% dependent on the rate of appreciation, and my crystal ball is pretty fuzzy as to what that's going to look like in the next 5-10 years.

It will help you track things more clearly and you'll be ahead of the ball come tax time. 

I don't have a crystal ball to give you a timeframe on any of this but take it from somebody that's lived a lot more life than you.

Cash flow is also profit, but tangible profit....and, it the property didn't recover, which profile would you rather be in:A)  Financed with only 20% down (own money), and only have to recover the down payment to break even (since the tenant(s) are paying the mortgage for you)B)  All 100 % cash/equity, and have to recover ALL of your "purchased" equity before you start making a profit.

Its not used because, and at least from my limit experience, I've never come across two investment that had such similar characteristic that I needed to get that level of precision in my measurement.

It is the economic hub after all. if the precises are challenging try Hamilton, Tauranga and Wellington. 

Any advice to break through and get the ball rolling?

I am looking to meet people, learn as much as I can, and get this ball rolling!

What about all the unknowns that pop up and throw a curve ball at the most sophisticated & experienced investors.

If so, it's not an offensive baseless low-ball offer.