What would you say defines a C or D property?

[Andrea Jones]

For me ( a lay person still), a D property would be one where several homes in the neighborhood are boarded up, plumbing or siding has been stolen, any graffiti inside or out, or I would feel unsafe walking around during the day. Those properties seem easy to define. 

The C property is what I think I would like to invest in for my first property or two. However, I'm not sure how one would define that type of property?