Have a 2009 iMac OSX Yosemite can you help me get the Apple ID or password
I bought a 2009 Mac OSX Yosemite and the previous owner does not have the Apple ID or password how can I retrieve that
You cannot.
The person associated with the Apple ID migt be able to recover access.
If you forgot your Apple ID password - Apple Support
If you forgot your Apple ID - Apple Support
How to use account recovery when you can’t reset your Apple ID password - Apple Support
Contact Apple for help with Apple ID account security - Apple Support
I would return this Mac if not, as it’s going to be a hassle and a risk to deal with,