Excuse my ignorance, but what formulas should I use to find those numbers? 

@Nick Ferguson,I think the heart of the matter is that you should find the formula you are most comfortable with and stick to it. 

Using the famous "wholesale formula": ARV ($440K) x 0.65 = 286K - repairs (35K) = $251K. 

Just use the formula above for a general guideline.

I am looking for locations & markets that can yield that formula. 

You will have to check with a CPA to see if there are formulas for it.https://99deductions.com/d/utilities-tax-deduction#airbnb-host-renter  has some info on that very thing.

Does anyone have a formula they can share.

My favorite formula thus far is; ARV = Estimate of Property Cost x 60% - Repairs - (My Fee x 2)EXAMPLE: $65,000 x(60%) = $39,000 - $15,000(repairs) = $24,000 - $10,000ARV = 14,000However, offering $14,000 for a property valued at $65,000 seems way out of the ballpark and not even the most motivated seller is going to be willing to accept that deal.

In other words, records must be maintained "in a manner so that the assets of the series can be reasonably identified by specific listing, category, type, quantity, or computational or allocational formula or procedure."

We do a lot of this work, so in many cases we already have the formula and simply need to check measurements and panel limits (electrical limits).