How to factory reset a password-protected used iMac

If it is not a firmware password lock, then you can try booting to the macOS installer (Recovery Mode using Command + Option + R, or USB) and using Disk Utility to erase the whole physical disk (or Fusion Drive if it has a Fusion Drive). Within Disk Utility you may need to click "View" and select "Show All Devices" before the physical drive appears on the left pane of Disk Utility. Erase the whole physical drive (or Fusion Drive) as GUID partition and MacOS Extended (Journaled).

As long as there is no firmware password lock and the device is not locked by FindMy, then you should be able to wipe the iMac & install an OS of your choice (macOS 10.6 - macOS 10.13).

Password protected as in the password for the local user account or is it asking for a PIN?

If it's a screen with a padlock asking for a PIN code, just toss it in the recycle bin at your local electronics store. There is no way to bypass that.

A lot depends on how thorough the previous owner was during his/her setup.

See what you might be able to achieve using the guidance provided in this article:

If you forgot your Mac login password - Apple Support

The seller should have set it up according to What to do before you sell, give away, or trade in your Mac - Apple Support  . If it's not setup this way unless you can contact the seller and get the password you're out of luck and it should be recycled.

Never purchased a used Mac unless it's from Apple or from an Apple Authorized Service Provider or OWC (MacSales.com).

If the Mac has been prepared for resale properly it will hav e this screen when first booted up:

Dragonfli67 wrote:

I cant get in to connect a mouse or keyboard.

Use a wired USB keyboard & mouse. If that doesn't work, then your iMac is in bad shape.

Dragonfli67 wrote:

Ok. Ill try it. I need to find one first. Thank you.

FYI, if you use a Windows keyboard.....the Windows key is usually the same as the Apple Command key.