How would you determine ARV for this property?

[Kyle McCorkel]

I'm looking to make an offer on an off-market BRRRR deal. The property has 2 separate buildings on a (small) parcel that normally would just have a single, detached home.

The front "normal" home is your typically cookie-cutter 3 bed, 1 bath.  The back house is 2 bed, 1 bath.  Both are in good shape and are solidly built.  At first I thought maybe the back was a converted garage but that is not the case - it is a legitimate 2nd house.  They are both on separate utilities as well - which will allow me to cash flow like CRAZY.

It is zoned as multi-family.

There are literally zero comps within 2 or 3 miles of this property and I've never seen anything quite like it around here (Central PA / Hershey / Harrisburg).  Would you use 2 unit properties (which are attached and share utilities) as comps, or would you use 3 bed, 1 bath single family comps, with some kind of adder for the 2nd house?

How would an appraiser look at this?