Does "Seller: Avis Budget Group" on a listing tell me anything about the title status?

It tells you the vehicle came out of a rental fleet, not its title status — fleet vehicles from companies like Avis or Budget are very often clean-titled, since they're typically rotated out for resale on a mileage or age schedule rather than damaged. As always, check the dedicated title-status field to confirm rather than inferring it from the seller name.