In my country, a brand new Quest 2 costs around $600 USD, so buying used is my only option. I found this guy on a trusted website that claims it was used three times by his cousin and then left to gather dust. I asked how long ago he bought it, and he replied it had been two to three years since the purchase. It’s going for around $330. Note that I do plan to use PCVR. Is this a good deal? Thanks in advance.
Honestly, age doesn’t matter as much as usage, and the Quest 2 is still highly regarded in the VR community. If it’s a trusted site, I’d say go for it! Just make sure there’s a return policy in case of any damage. 
You can’t even buy a new Quest 2 anymore. I wonder how much a Quest 3 would cost you.
There are zero used Quest 3s at a reasonable price right now.
Make sure the battery works fine. It hasn’t been used in a while, so verify that it’s in good condition. If you can’t find a better deal, get it; it’s still a great headset.