You can find CZO info here:  https://czo.nola.gov/article-15/From what I have been told any multifamily with 3 or more units is required to have a fire suppression system, unless you do townhouses and place a firewall between them. 

The county stated in order to make the home a two family I would have to install a firewall between the two halves.

Free Advice: Create two LLC's one for flipping and one for your passive as this will prevent domino effect if one aspect fails and make sure you setup proper firewalls to prevent commingling funds. 

The county's web server can utilize cookies, encryption, redirects, javascript, json responses, firewall rules and many other means by which to make scraping difficult.

And if you really want to do it right you have to put each one in an individual LLC, as the whole point is to build firewalls between your assets.

Much less expensive to build duplex's per s.f. cause you avoid firewalls, sprinkler systems, ada requirements etc.

Was the odor seeping through shared vents or through firewall or what?

Larger buildings have fire alarms and sprinkler systems; fire walls; wider hallways and stairwells with double exits, etc ... all measures to increase the available window to exit a building in the event of a fire.

VMware, Data backup, Firewall, Routing and Switching.

Some even have fire walls between them.