I love the city of Detroit. Not only as a wholesaler, but as someone who has spent a lot of years involved in the community. There has been a lot of changes and a lot of potential for growth. That being said I'm going to sound like a broken record...there are good and bad parts of the city. You have to know those area. If you're looking for stellar returns avoid the super hot areas like downtown, midtown and new center. If you can find a deal then good for you. There is a lot of development, but the prices are staggering and motivated sellers are nill to none. Look for good communities. Streets that have long term neighbors, cut grass, nicely landscaping, kids playing in the streets, etc..
The issue I find is that some out of state investors use Google Maps (pin drop) and take a virtual drive of different neighborhoods, but if you look at the date of when it's taken (top left of the screen), some of the areas were photographed in 2013 or earlier. Some of the neighborhoods look completely different now. It helps to find people on the ground and familiar with the areas.