I have standard inspection periods and terminate immediately if the condition turns out to be far worse than expected with repairs exceeding original estimates.

Rood and siding is in good condition, and the first major expense I see in the next five years would be replacing all windows. with a 15 year mortgage, at 5% (I'd rather budget high than low) cash flow would be 6056/year.

You need to visit the property for yourself to see the condition.

I guess it must mean something else because if the comps are $130-150k, it seems like the owner should still be able to get more than $35k by selling it on the open market, even if the interior is in less than desirable condition.  

It is honestly too hard to tell given I don't know what original site conditions look like, how much dirt has to be moved, are they having to import water to assist in compaction, how much excavated fill will have to be disposed of off site, concrete costs per cy including all fees to deliver, rebar costs, pumping or no pumping, -- looks like you are going to have 2 mobilizations,,,, one for the footing and the second to pour the slab..... there are a lot of variables here..... 

I have no problems stating that they know their business, understand the market and in many cases, for certain areas, literally know building-by-building who owns it, when it last traded, the condition of the property, the tenant base, etc, etc.

5% to 25% based on age and current condition.

This can increase price up to 340.

The condition of the property is a good starting point, but wanted to see what tools other folks use. 

FYI all Philadelphia Real Estate Investors -The Philadelphia County Transfer Tax Rate is increasing January 2017 from 4% to 4.1%.