I have purchased all of mine existing and then fixed up because as @Dan Heuschele said, ADUs are expensive to build.

Finally, like Natalie pointed out, your tax returns are your gold. 

Closing costs are huge - mine were about 2.5x my down payment.

I'm trying to not over think this, but I'm getting dangerously close to paralysis by analysis  :-)Another option I have is partnering with a friend of mine to increase our purchasing power to $1,000,000. 

Mine was that I should be able to pay off the mortgage in 10 years from the cash flow with 20% down.

Mine is nowhere near the amount you're refinancing.

In the mean time Gold & Silver are always a good option.

Mine is over 900 miles away.

There is only 1 fourplex near mine and nothing else around it.  

If you can offer them several times the interest they're currently making, they're more likely to be interested.And treat your lenders like gold.