Thank you for reaching out to the Community! You can add a user onto your account with different login information by taking a look at this helpful article here. I did want to mention that Constant Contact accounts are designed for single businesses to schedule out newsletters. If you want another business to send emails through your account you have to change the header and footer within an email. You also have to make sure you don't send to the wrong contact list. I do recommend taking a look at becoming a partner instead. It sounds like this would be a perfect fit for you and this way allows you to easily manage multiple Constant Contact accounts with separate lists. Thank you!