What is wrong with Warren MI?

[Andrew Nordbeck]

I have been searching for markets to make my first real estate investments in. I am strongly considering Warren MI as that place because of the lower barrier to entry(I can invest in several properties right away),  cash flow positive, and the newly built Amazon distribution center. 

I was very excited until I listened to David Greene caution against investing in "cash flow mirages." He specifically mentioned Detroit. He did not give any reason as to why this idea of cash flow is mirage here. Can anyone help me understand why this may be a poor investment on my part?