If I opt for annual plan creative clound I can host 5 sites. These sites have the subdomain businesscatalyst.com or can I use my own domain (eg. mysitename.com) I have to pay the extra monthly fee for hosting with my own domain?
The included service with Creative Cloud is the webBasics option. Correct, they will be associated with a service related domain initially but you can change them to your own domain and there is no charge for this.
Note: the domain registration portion is not included.
These might be useful for you as well
We also have the following article for Creative Cloud users, as to how to redeem your included site(s): http://helpx.adobe.com/content/help/en/business-catalyst/partner/upgra de-temporary-site.html
Also, we have a separate Business Catalyst forum specifically for that product. I'd recommend posting there if you have follow-up questions.