If the number is too high, you renegotiate the purchase price or you change your exit strategy.BP has a good book on the methodology for estimating rehab costs (I'm the author):http://www.biggerpockets.com/flippingbook

We recently had massive flooding in our area due to an ancient infrastructure combined with massive rain.

Your role is to apply the best methodology to a situation, solve problems and profit.

The methodology that most use is purchasing the property in your name then transferring it to the LLC.  

the methodology of deriving this number is explained here

I employ the same methodology.

So, when I finally decided to quit my career and start my own real estate investment company, I had all of these...mechanisms and methodologies...engrained in my head as the right way to approach any problem - PARTICULARLY, the right way to run a company (and I still believe this is true).So, through my real estate journey, I have noticed that most (not all) real estate investors don't really like to, nor see the need to, approach investing from a bigger picture.

 Your question is really bad since there is no consideration to type of accounting methodology usedI am going to assume your company (partnership, llc, S-Corp ) uses a cash basis accounting for the building and not accrual accounting (example and explanation here http://www.nolo.com/legal-encyclopedia/cash-vs-acc... ) since the furnace is considered a relatively large capital expense in the differing methods would be treated completely differently.Also did you use any form of financing on the Furnace?

Forgot to mention - I probably saved $10-15K on the purchase of that house due to the ancient furnace and asbestos.

Along with all the ancient TV tackle.