Can a sellers existing AdSense account be transferred to a new buyer?
An AdSense account cannot be transferred from one person to another. If a website is sold that has advertising via AdSense as a revenue source, the new owner will have to create their own new AdSense account in order to have advertising present. Please note that all new accounts will be reviewed and approved by Google and this approval is at Google's discretion.
Google AdSense accounts are used to provide advertising to a website so that the website can generate revenue by visitors to the site looking at or engaging with that advertising.