Are the clients and freelancers in different tables/tabs in the same base?
It is possible to do automatic linking based on email addresses using Airtable automations. However, there are some details that would need to be worked out. For example, if the email address is not the primary field, you the automation would require a scripting action. If emails are typed manually, you will also need to have a trigger that ensures that the address is completely entered before the automation runs.