What Are the Major Value Aspects of a Rehab?

[Dustin Smith]

Hey BP Nation, 

I'm going to show my newbness a bit here.  I've never done a rehab project, and never built a house, so I'm wondering what are the major aspects of a property that create the value on deteriorated properties?  Is it a good foundation?  A structurally sound roof?  Solid framing?  Good exterior?  There are several properties I've been looking at in my market that are clearly vacant, some of which are less than habitable.  Another way of looking at it, what do the rehabbers out there see as automatic deal breakers?

Thanks in advance!