ADU appraisal and valuation on BRRRR Questions

[Nicholas Spinazze]

Hey there Bigger Pockets community! My wife and I have plans to build to build a 3BR single family and an 2BR Accessory Dwelling Unit(ADU) on one of the lots we split recently. Our plan is to use the ADU as a short term rental and the single family as a long term rental. We had planned something similar to a BRRRR except we are creating value by building as opposed to creating value by rehabbing.

The trouble is the way lenders in this area value ADUs. They value them at a flat 90k regardless of the condition or rentability of the unit. The ADU we are building costs approximately 150k to build and has a significantly higher cost per square foot for construction than our single family unit. Our lender said that after a year of seasoning we could come back and they would evaluate the value of the ADU based on the cashflow it generates.

So it would take approximately 2 years to get the total amount of our initial investment back and I don't have any guarantees that they will even value it at its cost of construction. We are also concerned about how the buyer's appraiser is going to value the ADU if and when we choose to sell the property. As having the ADU is taking our value per square foot down from $235 psqft (which is what the single family appraised at by itself) down to $189 psqft.

Do other areas value ADUs the same way? Given all this does it make sense to build an ADU still? We haven't broken ground yet so can we go back to the bank and tell them we just want to build a single family now? Greatly appreciate any thoughts/advise/opinions!