How are small multi-families appraised?

[Jason L.]

I own a duplex that I am kicking the tires on refinancing. There aren't a lot of apples to apples comps in that area for other duplexes that have sold in the last year. I'm wondering if that meant they might use single family homes as comps? 

For example, the duplex is a 2/1 house with a 1/1 mother in law suite in the back (legally zoned for multi). Do you think an appraiser would just use a 3/2 SFH as a comp or might they just use some sort of gross rent multiplier?