@Melanie Hartmann, No matter the term you use to describe what you expect something to sell for, that term  will always be an imaginary/preliminary figure. 

I have also used it to do preliminary "back of the napkin" analysis for RV parks.  

China wage rates have increased 240% in the last 12 years.  

Here are some examples: (1) one of my clients buys 25 - 30 properties a month, he would never pay attention to a ranking on markets because he knows the towns he buys in, which has helped make him very successful (he's worth $20 - $25M USD), (2) my partner did some preliminary work for a hedge fun, they were looking to drop tens of millions of dollars - for them market trends mattered a lot because of the amount of capital they were deploying and the time horizon of the investments  I realize that I am not answering your question, but I hope that the above is useful as a frame work.

Investors are repaid as stated and I retain 100% ownership of the property and rental income.At this point, I have had preliminary meetings with some of my friends and family on my core list to gather interest about investing in my plan.

The BP calculators can be used for preliminary analysis (at least for rental properties).

Not sure how it will work out but preliminary results indicate significant improvement.You should discuss this with @Craig Curelop.

Taking longer holding costs out of it, I’d wager I’d still be paying a good chunk more for materials.

Many architects are willing to charge hourly rates to determine this and it should take less than a day.The more detailed the information you require, the more accurate the number will be, but if you are running preliminary numbers to find a great new build project, having an architect you trust on 'retainer' could be well worth your while.

I plan on offering him $40,000 based off of the condition of the home and what it will take (my preliminary rehab projections $70,000ish) to bring it back to life.