Running Comps as 2 semi-detached vs. a duplex

[Dhaval Sheth]

Hi, I am in the middle of negotiation of buying my first duplex property for BRRRR deal. It is a semi-detached duplex and the layout of both units are the same. After rehab, both units will look exactly the same. The issue I am having is I can't find any comps in the area for similar duplex property but can find a lot of 1-unit semi-detached comps that are similar to each unit. My plan is to refinance the property as a duplex to save the closing cost. Should I be safe to assume that the ARV of duplex will be double the comps of a single semi-detached property? How would the appraiser run the comps if he/she can't find a duplex at that time? This will be my first duplex property so I am unsure about this.