Hi Frank -
I'm curious about this too in regards to my 3 family. I posted a similar question and it was deleted without being answered. I called the NYS tax hotline and received two different answers - one saying use the full amount, one saying us 1/3rd. I've also asked around and nobody has a definitive answer.
If I had to guess, logically I'd say that you only apply the portion that represents the space that you occupy because your tenant can also apply for the credit based on the fact that his rent goes toward your property tax -- theoretically.
J
