eBay is pretty good at enforcing their policy banning sales of medical equipment requiring a prescription. They yank any listing for a CPAP very quickly.
https://www.ebay.com/itm/404778680293
They even have a category for "Medical equipment > ventilators". If they do have such a policy, they enforce it very poorly.
Policy: https://www.ebay.com/help/policies/prohibited-restricted-ite...