Make sure to find out what price that electricity is before you buy a miner. If your going to pay half of it some older miners will lose money, or stand no chance at ROI. I personally pay 100 percent of my electricity for miners, and becuse of price I need to use a S9 or I stand no chance at ROI. So it can make or break you.
But ebay is a great place I have sold most of my previous gen miners there. I have done a few on the board but ebay brings more a lot of the time as a seller, as there is risk of bad buyer's. So go into ebay knowing lot's of selection for using paypal to buy but you will pay higher then direct from Bitmain or from forum BST thread. But again with paypal as buyer you get paypal protection .... so it's pretty powerful protection in most cases. Also keep in mind heat/sound when you buy a miner. These are something I don't see mentioned that can be a big issue depending on where your mining.