When is a STR/MTR by the ROOM then make your resident an investment property?

[Lisa W.]

I know Primary Resident is when you actually live in the unit for majority of the time.

Q: If I rent out a room in my primary resident, is there a percentage (i.e. 2 rooms rented out of 3 or sqft, etc) that then makes the primary residence qualify as an investment property?  

Or, is it a dead fast rule that if you're living in it then it's a primary residence (period).  

Thank you!

[Colleen F.]

@Lisa W.  your primary is your primary as long as you live there. The percentage is the percentage you depreciate if you are renting for tax purposes.  You have to ask a CPA but depreciation is on the portion you are renting so a shared area I do not believe you depreciate.   

A lot depends on why you are asking the question. I assume taxes.