Anybody have any advice on getting accurate estimates for this?

Share profit & loss accurately based on the ownership split.  

I realize that I have to get more accurate number prior to making a deal, but I need to learn how to analyze a deal that will allow me to make an offer.How much do you think you can push the rents?

I would like to accurately estimate ALL of the costs here because we dont know what we dont know.

This isn't relevant to all markets, but for mine the tax assessment is actually pretty accurate with the sales price generally being within 20%.

Now it is worth 10x what he bought it for (based on my cost estimation software I use in my industry and knowing the cost per sq ft very well in my area, I am inclined to believe he is very accurate), he states he just wants X dollar amount for it and even after the gifting of the down payment, there is easily enough equity remaining to make that happen.I don't ever want to acquire or amass wealth through shady deals or taking advantage of anyone, so I know the statement of two players playing each other is a false one.

Would anyone be willing to pay for an accurate rehab estimate?

My point, though, is that while it's not entirely accurate, it's not as entirely useless as some would have us think. 

This might be a rookie question but I never had anyone clarify it for me, Is Zillow accurate ?

@Joshua Baker, Definitely you make a good point about retail being harder to lease these days, and I can see how building 250k of office/retail would be a big gamble.