how do you evaluate two homes on one lot

[Donald Banks]

I have a deal where the owner of two SFH's wants to sell but both homes are on the same lot. Is one considered a guest home and how do you appraise the value of each?

[Michael Herr]

There are a couple of those around me.

Two homes on one lot is less insurance and taxes than two similar homes on two lots. 

Generally water/sewer is combined,  so that generally makes it a landlord paid utility and chtge rent to offset. 

Selling could be harder,  because your end buyer needs to want inlaws quarters or income property. 

For me for  long-term buy and holds,  I  see it as a positive, except that (in my area)  it generally means one or both of the houses was built by a homeowner(or converted garage)  living in the other one.