I could see the bank wanting the ADU back if they feel the ADU was supporting the appraisal.  

Imagine my method a way of appraising companies instead of locations.

They purchased it for $3m, put $750k into it, we expect it to appraise for $5m, and are seeking loan proceeds of $3m.Here are three commercial mortgages that might be a good fit (click to enlarge, if necessary):Not listed there, but from left to right: Points are 1.25, 1.5, and 1.Prepayment penalties are 5 years, no, and no.The way to read "3/25, 15 years maturity" is that the rate is fixed for 3 years then adjusts, it has a 25 year amortization, and a balloon payment at the 15 year mark. 

An appraiser would lean on the "income approach" to come up with a valuation.

If you have completed rehab to support using the appraised value vs. purchase price to determing LTV, yes.

Appraisals were mailed to us (3 copies) in paper form with actual photos pasted onto the appraisal.

ADUs or carriage houses are well supported in adjacent downtown neighborhoods but no one is building and selling new construction homes the comparable will be very limited. the appraisal will be difficult. it's just a lot.

Appraisers and inspectors are not bound. 

Mind you, all of my properties are worth more than their appraised value now, but during the Recession the City Manager got the bright idea that the way to easily raise revenue was to raise the appraisals, and they ended up higher than the resale value of those properties. 

The appraisal came in at $120k where the purchase price was $78k and $22k reno cost for all-in of $100k.