Is there a formula based on revenue that is generally accepted?

From the countless failures I have experienced and the guidance of mentors, I have discovered, distilled, and applied this formula.

Maybe another entire month of rent is lost.Before you ask, I can't give you my formula because it wouldn't make sense to you without a long detailed explanation as to why, but that wouldn't matter because every investor has their own minimum...all for different reasons that make cents dollars to them. 

Valuation on large multifamily is based more on income, so there are formulas to run the numbers, versus single family where you are working from comps. 

A good ball park formula for Operating Expenses (OpEx) is gross rent * 30-45%.  

I think the sites and their estimates are pretty impressive considering they contain virtually every home in America, often with interior pics, but they are what they are: free tools that used automated formulas to predict something that can often be a bit unpredictable and can't fully account for the human emotional factor (for example I bet something like the Brady Bunch house zestimated far less than than its actual value)

We're hoping to get something going in the US  with a formula and strategy that works and replicate again and again!

BUT... you need to be somewhat sophisticated and be able to use formulas like IRR, PV, Lookup Tables, etc.

Your buying formula should be something like: ARV * 70% - Repairs - Wholesale fee = Offer

As they are written, those formulas are logically circular (i.e.