How does "make money when you buy" apply in duplex investing?

[Thuy Pham-Satrappe]

I'm having a really hard time establishing FMV/ARV when I look at duplexes because good comps seem so difficult to come by. (They're either a long time ago, far away, not comparable size/year/amenities) etc.

I run the numbers to make sure that it cash flows and I get the ROI that I want but I'm always hearing "make money when you buy" and "find a great deal"

Part of the concern with figuring out the ARV is taking into account the possibility of getting a loan on the property if I decided to do delayed or cash out refinancing because the ultimate goal would be to BRRRR.

Any suggestions would be greatly appreciated!!!