They rarely provide contact info, almost always call from some kind of bogus number showing a local(ish) area code, and then they ask me about 100 questions about my property which they clearly haven't researched.

This book is much more recent and maybe they eliminated the 7 days rule from the tax code.

For me, that resulted in guests not getting automated door codes among other things. 

I believe you have your zip codes mixed up  The 100 block of E.

.• Relies on city-issued tickets and can charge property owners with housing code violations if they do not comply.• Increases rental registration fees from $35 to $70 annually, with a cap of $30,000 for multi-unit buildings.• Requires additional disclosures to renters and homebuyers about whether a home has an identified lead hazard.• Creates a Lead Safe Advisory Board, a Lead Safe Housing Action Board, a Lead Screening and Testing Commission and a Lead Safe Auditor to track the progress and impact of the law.

The zip codes I recommend near military bases: 78218, 78109- Converse, has newer construction homes that tend to rent quickly but some of the lowest priced new homes in San Antonio.

Median sales price for 27520 zip code is closer to $250k and rents currently ranging from $1200-$1800 for detached homes.

Do you have specific neighborhoods or zip codes you're looking in?

I'm not sure of that answer even though I've had two properties in the area (Area Code 20744) over the last 30 years. 

While you can increase your chances of NOT getting screwed with your zip code based approach, you will eventually get screwed because you buy in the City of Detroit block-by-block.Put another way, I can take you to the best zip code from your analysis and show you houses you'd be a fool to buy.I can also take you to the worst zip codes and show you houses that would be a pretty solid investment.