Cannot run Comps on a split property

[Andrew Yen]

Hello I have a potential deal. The issue I have is the owner wants to sell only a portion of his property. He has 2 houses on the lot. The address he provided does not show up in tools like Propstream or REI Automator. When I look on google maps I am able to find his property but not the house he is wanting to sell. How should I run comps for this kind of property? Thanks!