Gaming computer for one game? (Counter strike 2)

I do not know a single thing about computers but I want to get back into gaming, really to just play counter strike 2. i'm just not looking to spend all the money on a really nice gaming computer and was hoping I could get away on a budget.

if I had to be near the $800-1000 range I think that might be ok. But I would rather be around $600 if possible.

Is there anything on the used market that I can look at? Also, how do I know what Im getting is in good shape/working correctly?

sorry for the noob questions