Yes, we offer both to rent and to onetime installation to your server.
Yes, we give training and others tutorial documentation with videos. Usually we provide an online session but also when requested we provide onsite training, it can be in our offices or at customer.
The billing system is not built on the FreePBX platform. We providing realtime and rating functionality among many other converged billing features. It uses an external database to store the data but it cost you extra.
Yes, you get the minimum amount of modules with FreePBX package. The modules can be bought separately and added to the base platform at any time.