asterisk based voip-fax-billing solution

I'm looking a voip solution that can be installed in a CENTOS VPS, where I can offer Voip subscriptions, Virtual Fax and includes a billing system (with gateway integration like paypal for recurring billing). The voip handler must allow me to set PBX and autoattendants for my clients. And of course a small control panel for my client where they can set up basic functions as voicemail, forwards, e-911 address changes, virtual fax, etc. I have my Voip minutes and DID provider. If you have samples already working online, please, let me see or test those projects. I am web designer and know HTML and design programs, so I can do the design customizations. I've heard asterisk can handle some of these features, BUT I dont know Asterisk installations, Telephony techniques, etc. I'm in Need to expand my services into the VOIP area, so looking for an already FRIENDLY platform that someone have designed who can offer me the same concept according to what I have described in this ad. Thanks.