The 4-pt inspection report indicated that all the major systems were updated around 2015.

Also if you can find anywhere that it indicated 90 days, then it is 90 days. 

Sometimes credit is not indicative of their level of responsibility.

Because the volume of deals done in the group indicates they might be overpaying?

All indicators point to this being a criminal enterprise.

Personally I'd invest in other affordable-but-growing markets in the Midwest, which are currently seeing greater price appreciation and job growth than Detroit, while still having decent cashflow potential.But the Detroit MSA had its first population increase in decades this year, indicating Detroit has "bottomed out," and will only continue to grow from here on out. 

Instead, he insulted my profession as an ortho surgeon which indicates to me I was right about his videos. 

A quick google search of your state indicates the following regaridng timeline to give notice:30 daysFor tenants who have lived in the property for less than one year, or have a lease for less than one year60 daysFor tenants who have lived in the property for more than one year but less than two years, or have a lease for more than one year but less than two years90 daysFor tenants who have lived in the property for more than two years, or have a lease for at least two yearsI'd definitely touch base with an eviction attorney in your state to ensure you are not missing any steps and to have the attorney as a backup option in case the tenant does not vacate easily.

So, their credit score may not be indicative of them as an applicant.

A tenant complaining online might indicate that the property manager handled them appropriately, so be sure to ask the manager for their side of the story.7.