Any additional due diligence questions or red flags I should look out for. since its my first time to invest in multifamily3.

Both the daughter and Dad have excellent credit history but feel this is a red flag. 

Wide and deep question.

I’m currently working to narrow down a list of potential areas to deep dive.

The tenant finds out that the insurance company will be fighting this with their very deep pockets.  

More secure and stable than an STR (also less competition) but you aren't in the red like you'd be with an LTR. 

They city will red tag it and require you to upgrade everything and get a Certificate of Occupancy before you can rent it.

Heck go to the casino and put it on roulette wheel of black or red. 

Although I haven’t done a deep dive yet.  

There's nothing left to cover expenses so you better have deep pockets to cover maintenance, admin, turns, etc.If you think you can quickly improve rents to a point that covers your expenses and pads your pocket a bit, then maybe, IF it hits your return threshold.If you're buying cash, then the mortgage is not a factor.