How to value a duplex without solid comps

[Bryan Williamson]

How do you value a duplex when there haven't been many that have sold. My agent sent me comps of single family houses but obviously they have sold for more they aren't investments. Ultimately it's only worth as much as the NOI which right now with only one side rented 815 I believe with improvements there's room for increase but I'm sticking with 815 for value sake. 815-560 mortgage x 12 = 3180/165000asking= 1.9 cap rate Thank you in advance