When setting up Shopify Payments, it will require an SSN for the individual who will be responsible for the account. In this case, your friend would need to input their SSN as an EIN would not be sufficient. All income will be reported to the IRS under your friend until the account is changed. Meaning, your friend would need to report the earnings of the business under their taxes for each year they are listed as the account owner.
Let me know if you have any other questions.