We both currently own our homes for a couple years.

The answer is that even if you had a formula it doesn’t work if you move 5 miles from the current site.

I file jointly and we are able to put enough of our income into a retirement plan that we can be below 89,000 in income (including rental income).

In my business ( currently building out a 90 home project in Oregon ) I hired the GC to build per door..

But you're missing a key number, how much is the income?   

First 10 years I/O and fully amortized for 20 years thereafter..If it's full income verification, strong credit and a lower LTV you should be able to get there with a mild buy down..Check in with @Joseph Chiofalo for a quick second look.

Whatever rent income/expense we receive/incur, is it split the same % as well?

We have ~150k equity in our current home and are considering doing a HELOC to either purchase or put a down payment on an investment property.

And that leads me to where I am at now, currently gutting and setting up a plan to renovate the building.

Hi, I recently completed a gut renovation that converted a single into a multifamily where I currently occupy one of units.