SFMF & SFMF PRO | I have an active Aweber account, do I need to purchase another account or I can use my existing account?

You can use your existing Aweber account.

As long as you have a paid account that allows you to create multiple lists and campaigns; then you can use your same account. You do not need a separate AWeber account for SFMF OR SFMFPRO.

It is actually personal preference and unless you want to.