There are some formulas, so the ledger updates automatically for any item that you put a date in for.

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Or some formula based on NOI and book value for the property? 

Can anyone share/recommend an estimating formula or technique for calculating new construction costs?

You will have to figure out that specific county’s mileage rate and tax formula to project what your taxes will be.

Id bore you with the formula but thats why we have google.Sorry for the long response, but I'm here to answer absolutely any questions you may have.

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Because there are many variables that determine if pre-foreclosures are good deals, I'm confused about how the standard formula applies to them (ARV *.70 - repairs - assignment fee). 

Operating yield is a measure of NOI and NOI has a direct relationship with value.I wasn't really commenting on the mechanics of using the cap rate formula which has been beaten to death on here.