Unlike my current active stratagy on my 19 SFH,  I will not be able to recoup the renovation cost back out of the property value by having an 80% Loan to value pulled on the back end because the buy price is just not good enough.

I have found that if its a good enough deal to flip , its a good deal to keep as a rental , sometimes better , as a rental you do a quick repair and cosmetic update and rent it out , and in maybe a couple year it has appreciated , you then do a remodel and sell and you have made much more 

"I don't know" isn't a good enough answer. 

Assuming you don’t have electric heat you may need to run new gas lines and add a second furnace.Conclusion: I would only consider doing this if I was doing a significant enough rehab that I would be tearing out walls anyway and if the deal was good enough to cover the cost.

Where you numbers not good enough?

If it was good enough when you signed the lease it's good enough now." 

There are some folks doing well by using no points fannie financing for their flips, that have learned to qualify the property as juuuust barely good enough for fannie financing (but still messed up enough that it scares away retail owner occupant buyers).

Currently in my first house hack, a duplex I purchased in December 2022 for 444k with an 3.5% FHA, the property was in just good enough condition to qualify.

I totally agree that people should have reserves but how much reserves is good enough. what rules do you use to cover for this type of once in a lifetime event?

There's no problem with it per se, as long as it cash flows really well, that's good enough.