Thank you for all the responses. It is in Hollywood, and I believe it adds value, but I have found no comps with similar separate guest room. I have not inspected this property yet. So if I did an adjustment it would be across the board. The home is worth over a million around 1.1 not sure about value on the guest room with no comps to support adjustments.
Look for other similar rooms like a cabana, studio, office, guest quarters etc.