Detroit isn't zip code run, it's block by block, literally. 

Fine you checked the block, no fee.The service animal scam at the verbal level is just one of a long line of traits in potential tenants I do my best to avoid.

I had two properties surveyed a few blocks away in 2/2017 for $450 each.

The vending machine blocks the entire sidewalk.

And then pick a couple of neighborhoods  maybe a 2 mile be 2 mile block, walk/drive them and get to know what the prices are. 

Oh, and almost forgot, all of the units are within a couple blocks of each other, not sure if that makes a difference, but I'm still trying to decide whether to self manage or pay a property manager to do that.

I actually saw a crappy little dumpy house on Schmitz (one block north of Texas St.) go for $160K. 900sf!

A house down the block has cracks running vertically from top to bottom.I'm not sure if I want to risk another $500-$1000 for inspections if there is going to be foundation problems.Skip or submit contract?

Is it relatively safe to be looking at most houses in those 4 places or is it a street-to-street or block-to-block situation where one street is great for investment and the next one is a war zone?

It's the type of place where on this street you're great, but down the road a flew blocks you aren't exactly in a great neighborhood.