How does the city condemn houses?

I thought I read somewhere that the City / Detroit is going through the neighborhoods to see if houses are habitable. That if a house is uninhabitable that it being condemned? how does that work.
Scenario: Relative lives on the only house in the block. House is off the foundation. House is 100 years old, needs serious updates. Relative is determined to say in house as deplorable and Sh**TY as it is.
House probably needs to be inspected by the city or condemned. The whole block/neighborhood is nothing but brush and weeds. Here's what a patch of land looks like:
https://www.flickr.com/photos/830757...posted-public/