I think by the time you take all those factors into account like you are they will make any deal look like it wont cash flow.   

vlad, I would think you could dissect the comps more: square footage, locations, amenities and make some adjustments to get a ball park number .they may have been all over, but may help you make the "reasonable offer" if you can study them some and maybe get what  duplexes are going for on a sq foot basis in the vicinity, a factor which may still work in your favor as you will be newer and probably better conditon with a new/newer build...

Any suggestions on important factors to consider in hiring these individuals?

So if all goes well we will acquire cash flowing properties with little to no money considering it cashflows as all factors are factored. 

It does concern me that I can't walk through the property but I've tried to factor that into my offer. 

A big factor for this approach was that we were heading in the housing bubble and the numbers no longer seemed to make sense to us so we stopped buying.  

I can tell you that the office building is the most work by a factor of 10.  

Until you factor in opportunity costs as you'd have to pass on potentially great deals because you've tied up your cash in 1 deal.

@Joel M.The key isn't just that its a 30k home - its what other important factors are specific to the property to make it a decent deal or not.

So I imagine that factors into your calculations.