Asterisk as a hosted PBX for voip selling purposes

Good day ,
I am still very new to voip and this forum
I do have a very good knowledge of networking

I own a small Wisp company and want to start selling voip as well to my current and new clients
I have a supplier that can supply me a Trunk but I need to know more about Asterisk and its abilities because we all love open-source.

can someone point me to links of possible examples or tutorials to setup such a system using Asterisk ?
I need to add multiple clients and also small medium businesses.

Any information will be greatly appreciated

Best Regards

FIrst of all you should start reading and (which is based on old version of Asterisk but I insists to go through it to understand structure and concepts)
–Satish Barot