. - Chicago zoning & permitting is always a confusing topic. 

I have done both multiple times over the years but suing is usually when there is no other way to settle or they have tried to back out multiple times..... or i have put a ton of work into getting it zoned a certain way or land split approvals, etc....

No zoning issues with your proposed use of the property?

The house isn't in a flood zone.

Very specific areas are not subject to the waitlist, or zoned intentionally for their use. 

Are there any red flags I should be aware of, such as the vacancy expense or NNN costs?

Would I need to apply for a variance/get the zoning for it?  

We just went through it with a property that had multiple large red stains.

You might go to the planning and zoning office IN person, don't call, and talk to planning staff. 

@Kevin Lee Detroit definitely has some good spots like Birmingham, Bloomfield Hills also within the city limits of Detroit you could find opportunity zones and gentrification going on that could be worth while.