I'm thinking about buying a used MacBook soon. It will be my first Mac and I am looking for tips and advice about once I have the computer. What, if anything, will I need to do in order to make sure I am protected? Essentially, how do I make sure the PO doesn't have anything installed on the computer to allow them to still access the device or a keylogger or something that could bite me or my bank account in the arse later on. Likely, I will purchase a computer from a refurbish company like TekSavers or Gainsaver. I look forward to your advice and thank you for your time.