Current “As Is” Value: $625K.

The mortgage guy told me the other house would be treated as an ADU and give me no real value towards the value of my future mortgage.Not sure if that helps much?

Issues 1) even garage conversion ADUs in single family zoned areas typically cost more to build than the value that they add.  

Also what does the city say is the assessed value of the property on your taxes (it will be different than the appraised value, but should give you an idea).

Refi after construction.These numbers consider only the portion of costs of the HEL attributable to the land purchase, not the payoff of the HELOC (which we took out to buy the Seaside condo).Cash In:                     $66,166 (Cash, 1 year of debt service of HEL, debt service of const. loan, furnishing)Amount Financed:      $548,000 (home equity loan + construction loan + closing costs)Total Cost of build:     $614,166ARV:                               $850,000 (or rather "after construction value")Refi                                $637,500 (75% of value + closing costs)                                        Cash Out                       $89,500New payment             $4500/month (54,000/year)Estimated Cash Flow (pre-tax numbers, so actual mileage may vary)airBNB year 1:            $70,000     (net income $16,000)airBNB year 2:            $100,000   (net income $46,000)airBNB year3+:           $120,000   (net income $66,000)ROI (construction year):    0ROI Year 1 of STR:              24.2% ROI Year 2 of STR:              69.5% ROI Year 3+ of STR:            99.7% Did I calculate these ROI numbers right? 

Pay others when they’ve provided value to you.7th - Prime is not smarter than your local folks who you can have real relationships with.

Some lenders will do a 2nd, up to 89.99% loan-to-value, which in your case would be about another 122K3) You will still need to pay the remaining 10% as a down payment.

Really what I am trying to figure out is what is the ratio of value for the various things that different partners would bring to the table like: down payment, long term management, rehab labor, acting as contractor for rehab but not doing the work yourself.

Current "As Is" Value: $770,000.

How are you arriving at the $120k value?