For canvas App:
While exporting the package, make sure he selects "Create as new" as an import setup.
Once he sends the Zip file, you can import it then you will become the owner of the app
For Portals:
My below reply i.e. you need to create an office 365 account, assign a security role, and a license.
Hope it helps.
------------
If you like this post, give it a Thumbs up. Where it solved your request, Mark it as a Solution to enable other users to find it.