in my opinion, you are in grey water, because depending on where you live, that pump may have required a prescription. If the pump required a prescription, you may not be allowed to sell it in the US, even if you paid in full. When I think of potential liability…(infection, injury, death) that a person who paid you money for your pump and then was subsequently injured…my head starts to hurt.
one thing to do would be to check with hospitals/medicare. Medicare routinely re-issues used pumps.