You cannot transfer purchases - those are permanently tied to the AppleID used when making the transaction.
For iCloud content, see Winston Churchill’s post in this thread fro a guide to do that - How to transfer all files from one iCloud… - Apple Community
Also note if you share an AppleID for FaceTime and messages, you’ll both be getting all of each others calls and messages.
You may be far better off simply setting up family sharing rather than trying to share an AppleID, which means sharing everything - messages and texts, notes, iCloud email, contacts, call history, etc. There is no privacy nor separation of any data when you share an AppleID for Apple online services.
Set up Family Sharing - Apple Support