House Hacking - Definition of Primary Residence

[Joe Jor]

From a mortgage perspective, does anyone have a definition of what "Primary Residence" is and how it is tested?  Putting on a pseudo-lawyer hat, I can think of multiple interpretations:

• Location where you sleep
• Location where you spend the greatest number of hours
• Address used on taxes

There are probably hundreds more ... and I can think of many exceptions to those above.  I look forward to the ensuing discussion.

Joe