They can change quickly and, as you'll hear, Detroit can be very "block by block".That said, there is a TON of opportunity if you understand the landscape and what you're doing.

@Gabriel Mesa Fairly straightforward in the suburbs.In the City of Detroit you can NOT use zip codes, you can use Neighborhoods if you know what you are doing, but you need a trusted local to check out block-by-block to finalize decisions.Since there's a lot of rentals in the City, you also need to decide BEFORE you start a rehab, if you are targeting selling to a landlord or an owner-occupant buyer.- You tenant-proof a rental, but need higher finishes on an owner-occupant.

You can consider installing individual boilers for each block.

It is a really big city (sprawling-not very centralized) and it changes a lot in a few blocks.

I actually live a few blocks away, and own several properties around the West Side.

I have heard of people staying long term then cancelling their booking consequently resulting in a blocked calendar and no pay. 

-- and someone more cynical who has been around the block a few times might say "yeah but Edward Jones is a solid tenant, that's super low risk, and they've been there for 15 years already, and are 2 years into another 15 year lease." 

I found a bunch of info but can't post it as the site is blocking links.Having said that, there will always be someone who's asthma is severe enough it will be triggered.

Could one buy a pool of mortgages from FNMA, split that pool back up into individual mortgages,  then negotiate with the homeowner to purchase their own mortage at a discount, removing a huge stumbling block in the real estate market.

If this was a piece of land in midtown or downtown that would be totally different than a piece of land on a rough block in the east or west side of Detroit.