I would not use zip code to determine neighborhood class in any state. 

Many of the neighborhoods are still worth the investment, though they do struggle with seasonality.What specific ZIP code are you considering?

Hello, I wanted to get feedback and thoughts from Investors and Real Estate professional on a potential tool that would use machine learning and AI to create scores or ratings on real estate markets at the zip code level.

See https://library.municode.com/tx/killeen/codes/code_of_ordinancesChapter 26 is known as "City of Killeen Subdivision and Property Development Regulations."

Four months ago, we bought a house in Decatur, zip code 30032.We thought we had everything sorted when we hired a contractor to rehab the house.

Converting into a duplex could be a good idea after you move out, but once again, I would double check and triple check zoning ordinances and codes to be compliant. 

Stair to basement no railing, not to code.

Per code, as-of-right, a building with a CMX-1 zone designation is permitted a maximum of two or three dwelling units (dependent on lot size) plus any applicable housing density bonus pursuant to section 14-702(7).

Also we created a free Memphis zip code guide that I can send you if you DM me. 

My (unsolicited) general philosophy is to wait to buy anything until you can confidently say you are one of the top 5 experts in the world at any specific zip code.