What's a free billing software for commercial use?

There is a requirement of free billing software for commercial use. After the satisfaction i.e ater the trial version expired I am ready to purchase it. My minimum requrement is like this list below:

Password protection for company files!
Unlimited...

customers, invoices and items!
Unlimited number of companies!
Create, email and print professional invoices!
Manage recurring billing cycles (subscriptions)!
Fully supports multiple users over a network!
Manage customer databases!
Manage product databases!
Send newsletters to my customers!
International currency and date support!
Charge credit cards over the Internet
Any information of billing software which fulfill my above mentioned purpose is welcomed here.

Hi,

Here are some names of software I found:

Excel Invoice Manager (very popular and recommended)
Bill Central Billing
kBilling
Billing Star 3
Time n'Bill

All of them are free to try, then cost money (Shareware)

Good luck!