How to calculate an ARV for a 4 units or less income property

[Andy Fernandez]

Good morning BP I have a big question:

I am looking for the correct formula to calculate the ARV on a fourplex. I understand the ARV of an income property is calculate as ARV= NOI/ CAP rate. If you need to do this calculation and you have your NOI but you do not have a purchase to calculate your CAP Rate what do you do ? ( I do not want to goggle a Cap Rate for the area where the property is located) what do you do ?

I am looking for a way to calculate manually ARV, in other words I need to know from where the number comes from.

Any help will be highly appreciated.