This decision increased our budget from $15K to $45K, but it turned out to be a wise investment.

If you can get your Vantage Score up 50 points, you will see positive results on the mortgage scores as well, it just may be 30 or 40 points or could be 60 to 80 point increase vs Vantage increase of 50 points. 

If your property's value has increased since you bought it... given the market trends in Albany, that's quite possible... you could tap into that equity sooner than you might think.

The plan is to use the heloc to purchase additional properties, and basically brrrr and pay back the balance - then repeat.What I didn't realize is how difficult it is to find a business heloc.  

My spreadsheet also includes FMV of every property so I can monitor appreciation, year over year comparison of tax & insurance increases, current rent & last increase & last amount, etc.

Looking for a house we could house hack, had an incredibly low interest rate on mortgage and house has increased in value about 42%, an estimated 180k in equity.

Your equity won't likely increase beyond the cost to build because there aren't a ton of ADU comps on the market yet. 

It's very difficult to find off-market deals with predictable upside opportunity.  

I am guessing stricter privacy laws can make this difficult.

If land values are increasing significantly, you can back-end load the seller financing for a percentage of the profit when you sell.To add to prior comment, how many septic tanks do you have?