Merge Two Laravel Sites into One Database

I need to merge two Laravel sites on a single server into one database. This will allow customers to register and pay on my betting site, but access it with credit on the other site.

Requirements:
- User Data Sharing: User profiles, payment history, and activity logs need to be shared between the two sites.
- Existing User Data: All existing user data from both sites should be merged.
- Database Setup: A single database is preferred for both sites.

Ideal Skills and Experience:
- Strong expertise in Laravel
- Experience with database merging and management
- Familiarity with user data synchronization
- Ability to work on a shared server

Please provide examples of similar work done and your approach to ensure data integrity during the merge.