I buy used iMacs and MacBooks (2013-2018) to upgrade and resell. Cracked screens are ok, not working ok as well. Just let me know model # (example ME086xx/A) or find it here https://support.apple.com/en-us/HT201634
and I can give you a cash offer.
Sure you could sell on ebay, but when you subtract shipping and ebay/paypal fees you may get half of what I can pay.
do NOT contact me with unsolicited services or offers