The city that assesses the taxes also uses different formula to come up with a value.When I bought my commercial office building, a bank contracted someone to assess the value of the property.

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). 

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.

Because none of the successful people would just share the secret formula they all used to get rich. 

I want to make sure I understand with an example:If I have a rental property that sells for $320,000 and closing costs/commissions/etc = $20,000 (round number) and I owe $100,000 then according to your formula I would need to purchase (exchange) for a property or properties that cost equal to or greater than $300,000 even though my net proceeds after paying off the mortgage would be $200,000

Also, I'm not sure how to determine pricing for things... would it be as simple as price per square foot to build or is it some other formula? 

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.

Thank you to everyone.Tim, I had this long response detailed out to get things down to a few conceptual mathematical formulas based on some of your points, but I deleted it. 

This limits what I can do for exterior renovations.Biggest advantages for commercial office space are tenants that will sign multi-year leases, less personal drama, and a simple formula to value the property.The biggest downside is the potential for longer vacancies.