Difficulty finding comps on a 4-unit

[Matt Foster]

I have a lead on a 4-unit complex and even going back 4 years there just isn't much by way of comps to look at.  This particular property is 2 buildings/2 units in each.  Given the lack of sold comp properties in this particular city (and similar nearby cities) would you then shift over to evaluating the property using the cap rate method?  Thanks in advance.