There could be $100K worth of functional repairs that you'd never know about just looking at pictures.All that said, the BP book on estimating rehab costs is a great place to start (I'm the author, so perhaps I'm a bit biased) -- once you understand the methodology for how to estimate costs and the specific process, it gets much, much easier as you practice.

I research the investment, the management of the fund, educate myself on appraisal methodology, economic forecasting, etc.  

Our methodology is B or C properties in A, B or C areas (slight value add).Key indicators we look for in our deals are (CCR = 10% or higher.....

As this is your true actual cash flow this is logical (although i am not sure i would call their methodology to calculate it logical)if it is negative, they consider it a debt obligation and thus it has to get added to the debt part of your DTI. if it is positive then it is added to the income part of your DTI. for a principal residence property: the same calculation is carried out except the PITIA expense is left out and the resulting number is used as your rental income. this is counter intuitive as it is not your actual cash flow at all, your actual cash flow is a lot less than that number, it could very well be negative but what is also counter intuitive is that the PITIA (ie the housing expense of the entire building) is added to the debt part of your DTI.

Just to give you an idea, we have hard scientific data about our Turnkey and the methodologies we implement have scientific results:Avg.

But be aware that there is a lot of push from some people to create a split tax roll in CA which would separate commercial property (which includes large multifamily) from residential property and strip prop 13 tax methodology from commercial properties. 

In 1977 they presented a joint paper describing a statistical methodology in risk assessment of lending to a particular consumer based on how the credit history of that consumer compared to the statistical norms of a large pool of consumer data in several key areas.

However, firms raise cash depends on the character of the business and therefore the methodology of entrepreneurship adopted.

If the tenants are paying for water on a 1-4 unit, that is a vastly different methodology used for the apartment complex owner. 

My goal is to build a portfolio using the BRRR methodology and position myself to where I can buy my own home.