Appraisers Approach to Two Homes One Lot

[Tyler Haanen]

I came across a property on the MLS that seemed like an interesting deal but it happens to be two homes on one single lot. I come across these once in a while but this is the first one that I have been interested in learning more about. For rehab and ARV calculation purposes, could any appraisers or those with experience on this explain how comparables are used to value these types of listings?

Follow up to that, does insurance also "double" seeing as there are two roofs, foundations, etc. to insure?

Thanks for your thoughts.