The appraiser will use market rents to determine a square footage price and then measure for square footage to determine valuation.Most lenders will require some sort of a profit and loss or at the very least an operating income statement to actually underwrite it. 

The defense of the 2% rule is that it is a rule of thumb which allows you to reject a property that doesn't measure up based on the numbers.When you're looking at a fix and flip, the rent is not a prime consideration, many times the property is vacant and often uninhabitable. 

Measure your results.

And 36 Other Key Financial Measures By Frank Gallinelli I am looking over it presently and have found it to be very helpful.

I have a print out that has all measurement of the walls.

Any key measures of metrics that would make sense?

I would suggest that you look at a lot of properties and learn the numbers behind real estate (read this book: http://www.amazon.com/Every-Estate-Investor-Financial-Measures-ebook/dp/B004BKIEUS).

Obviously, my purchasing decision won't be based on what I can find on one of the sites but it could be another measure to use.

And 36 Other Key Financial Measures"Search around the site.

After it's clamped measure diagonally from corner to corner to make sure it's 'square'.