I agree with you on metal hardware--if it looks and works fine, it probably is.
It's hard to evaluate a climbing rope by visually inspecting it, though. The strength depends primarily on the core strands, which are hidden away behind the sheath. Chemical damage is not as visible as people assume it is.
It's especially hard for lead ropes, because every significant fall takes some the elasticity out of the core. A rope can look perfectly fine even if it is no longer capable of absorbing a lead fall. The danger here isn't so much that the rope will break, but that the lack of stretch will overload your pro, your body, or potentially even the anchor.
So I would be very hesitant to buy a lead rope used, unless you really know and trust the person. Top-roping should be fine because the fall factor is so low. You can top rope with static cord if you're attentive to the belay.
It's hard to evaluate a climbing rope by visually inspecting it, though. The strength depends primarily on the core strands, which are hidden away behind the sheath. Chemical damage is not as visible as people assume it is.
It's especially hard for lead ropes, because every significant fall takes some the elasticity out of the core. A rope can look perfectly fine even if it is no longer capable of absorbing a lead fall. The danger here isn't so much that the rope will break, but that the lack of stretch will overload your pro, your body, or potentially even the anchor.
So I would be very hesitant to buy a lead rope used, unless you really know and trust the person. Top-roping should be fine because the fall factor is so low. You can top rope with static cord if you're attentive to the belay.