It happens all the time for multiple reasons.I’d say a typical tenant stays 2 years in a house and maybe 1-2 in an apartment, depending on class

They are also typically shorter termed - like 5/1 and 7/1 ARMs.

Long terms on commercial properties (5+ units) that are stabilized (typically > 85% occupied ) tend to be based on the property itself, not your personal guarantee.

After the 90 days are up, the flipper can now sell to an FHA/USDA buyer, but if the flipper sells it for DOUBLE of what they paid, then the flipper will have to pay for a 2nd appraisal to go along with the first appraisal that the buyer typically pays for.  

30-60k per door on your typical value add class c

Assuming you would buy the foreclosures from the county auction, foreclosures are typically harder to finance.    

Typical breakout is usually 60/40 but depends on the property.

Depending on size of lot and # of structures and impervious surface these typically are not cheap

How long is the typical due diligence on a property like this?

Typically it breaks in hottest or coldest day of the year and that’s when you will pay a premium price to get it replace or fixed.Personally I would not want to install a refurbished HVAC system, I think you’re better off w new installation and not have to worry about it for a long time.Typically when I purchase a unit and I know HVAC system is over 15 yo I know that sooner rather than later I will have to replace it and I plan for it..