I bought an I Mac of eBay with wiped HD

The computer may be too old to run Internet Recovery, IR only works on 2012 and later iMacs. If your machine is a 2011 or earlier then you will need to buy a $20 Snow Leopard DVD from Apple to get your computer going. You can find the link for the DVD at Mac OS X 10.6 Snow Leopard - Apple

Good luck!

What year / model of iMac exactly?

What happens when you try to boot to recovery?

Does the screen show anything?

You'll need to provide details about the computer before any one can help you.