Celebrate the beauty that exists (Michigan Central was actually what I was thinking of with the Rome comment) and take advantage of the rest. Do you know how cheap it is to live in the city? Yes: there are acres of abandoned rotting land, but what's keeping Detroit from turning it's warehouses into startups? Imagine SOMA on a city scale.
What's missing is the things start-up employee type of people are looking for in a city: density, diversity, transit, food, Asian girls...
The thing that people miss when comparing Pittsburg and other cities to Detroit is that it is square MILES upon miles of complete ruin. The "ruins porn" is good for the city because it raises awareness of what destruction can take place when you remove the underlying economic structure from a community.
In terms of "startups", you are free to do -- there are city taxes, but it's probably doable in some areas, but keep in mind the lack of city services and that it is still a very, very dangerous city.