BUT in vast majority of cases the % rate at which they are being assessed against the property value has laid flat or gone DOWN, not up. 

Since 2020 we've seen large asset value increases and large tax increases, and more modest insurance increases but we've been able to improve our profit margins sufficiently to keep up with inflation and even do a little better in many cases.

Instead:401(k) loans: They’re low-interest, and you’re paying yourself back.Roth rollovers If you can afford the taxes now, this gives future flexibility.Creative financing: I’ve seen clients leverage partnerships or seller financing to limit retirement fund withdrawals.One thing to consider: real estate markets today are vastly different from a decade ago.. so opportunities may require extra creativity.Have you looked into specific deals yet?

If the Ensuing damage is also not covered, the total loss could be vastly higher.  

Furthermore you can vastly increase your returns through leverage using a non-recourse loan but that will definitely trigger UBIT but again the numbers can still make a lot of sense. 

Isnt it sufficient using apps like Stessa or Avail or Rentprep etc etc?

The "online leads" trend becomes a vast pool of scams, each one discovering a new and "better" way to find motivated sellers via SEO/Paid adds/Social Media etc, and automatically aims to make a profit from selling those so-called leads.

One bad tenant can ( and have) quickly destroyed a year+ worth of profit.I agree with the vast majority of what you said.

The vast majority of these units I purchased using private financing with $0 out of pocket. 

Under $100k, were talking Old, beat up, it's coming with issues and the vast majority of time there is hidden uglies that come out later.