Paying off primary residence vs buying a rental

[Pete Linn]

I have 3k surplus monthly. I have been throwing into my primary residence at 6 % 30yr fixed. I own two rental property one is paid off and the other one is at 2.75% 30yrs fixed I don’t plan on paying it off early because of the low rate. My question is, should I continue to pay primary residence off or looking into buying my 3rd rental property? Thank you all.