Where do YOU start when YOU clean an old machine?
When YOU buy an old sewing machine where do YOU start? Do you sew with it or clean it first? Why? What do you clean first? What is your system?
Are you willing to buy a used machine someone has already cleaned up? If so what do you expect to pay? If you do clean one up what do you think is a fair price to charge? You can answer any way you like. I'm just curious.