Buying GPU from someone in Canada - do I have to pay tariffs on it? r/homelabsales

Buying a GPU for around ~$900 on r/homelabsales. I didn't see a place to ask there, so I figured maybe someone here might be able to answer my question since I keep finding conflicting information online.

I live in CT and I'm buying from someone in CA.

Would I have to pay a tariff to get part through customs? At what part of the process would I discover this? Seller will pack and ship card - would he be able to find out there? Or is it only handled once US gets it? I'm pretty sure I'd be the one paying tariff, not him, right?

Thanks in advance, and sorry if this shouldn't be posted here.