If market research indicates a particular area is losing jobs faster than the national average, has a low population rate to begin with, and has a higher proportion of owners to renters, along with other indicators of potential issues, then I may be able to reasonably assume that it will be more difficult to find good tenants, more difficult to charge market rents, etc.

I totally ignored them at first, but more and more they are showing themselves to be a surprisingly (to me anyways) good indicator of how much room for improvement a property has.

The only thing that comes to mind immediately is "water marks" on the wood hidden behind a wall in the basement which indicate it was previously wet and dried.

They indicated that there were no oil tanks on the property. 

I know you mentioned that the tenants pay water and sewer, does this also indicate that these services are provided by local/city utilities?

Try to have the contractors provide you an updated invoice indicating paid in full/ work completed.  

@Joseph LuceI agree with @Tim Gordon for the reasons he indicated. 

Don't spend every dollar you have in property one, if you can help it.As @Michael Lee indicated, if you have 400k sitting around, your options drastically change.

Not sure what your intentions are as you didn't indicate if this is a rental, flip or primary residence. 

If you are a licensed real estate agent as you seem to have indicated, it should just come to you through your brokerage.