1. when a user purchase service, ISP will provide antivirus service with internet connection if client want to subscribe AV service.
I agree with the above. You don't want to be handing out enterprise-level security software to home users. Also consider the licensing concerns; you would need to purchase a license for each of those users.
how can we recognize unpaid client in SEPM console hence there is no naming convenison use
There is no such thing as an 'unpaid client'--if you're using it, you paid to use it. There is no licensing file to revoke or restrict. It can't be controlled that way. Besides, in the case of Comcast offering Norton to their subscribers, I'm pretty sure Norton wouldn't stop working if a customer canceled their Comcast subscription.
2. how to stop sep client piracy mean SEP package can be instal one same machine user could not install on 2nd machine.
You couldn't. Again, not intended for home use.
3. Clieant want sepm integration with billing application database to manage billing system.
...manage in what way? Manage users based on paid status? Any such modification to the database would be completely unsupported.
I think you should rethink this idea...
sandra