Hello @GregDixon ,
The website can be completely built and published for free. This will, of course, include the constantcontactsites.com part and the banner; you can check out an overview of the free website plan here. If you're wanting to completely unlock and do more with the website builder, we do have a base paid plan for $10/month that unlocks everything. Additionally, if you already have a paid email / online marketing plan with us (i.e. Email or Email Plus), then you should already have the paid version of the website builder unlocked by default.
If you do wish to have your own domain in the future, those have an additional yearly cost associated with them (typically $20-30/yr), since that runs outside of our system.