I preach to everyone make a wish list, prioritize, test the software and double check. 

Take it with a grain of salt as safety is subjective.You could also ask your Realtor and property manager their thoughts and maybe next time they are in the area to take photos.

My preference is to prioritize longer bookings and STR in the gaps.

I would talk first to an electrician as many do fire alarm and life safety.

I don't think you are going to be able to get insurance for two separate living units in a single-family when they are both illegal and likely do not have the correct egress windows (basement) for fire safety which could subject you to huge liability if something happens to either party.

Like you we had 3 teams of two door knockers  2 for safety one women one man.. and we door knocked every NOD in our 2 mil MSA  all to boil it down to if we were very lucky to get 2 to 3 deals a month.. now we were a little different I only would buy very high equity deals.. and we leased back .. because as you state 99% don't want to leave.. 

Prioritize tackling critical issues and beefing up security to keep your property safe and sound.

With many advisers there is safety.  

Properties with low cap rates (5.3%) often trade because investors prioritize appreciation over immediate cash flow.

Prioritize your financial stability.