The easiest way to add VOIP to your existing data network is to buy a hosted solution. You simply pay to connect to the provider's network and they do the rest. But medium-large businesses -- and even small businesses with tech know-how -- are going to want to build out their own solution. Basically, you treat Business VOIP like any other data application. You connect it to your data network and use switches to properly route calls through your internal network. Setting up a Business VOIP network can be expensive, however. Even small-medium businesses can expect to pay five figures ($xx,000). But with cost savings of up to 90 percent over traditional PBX phone service, you will make it all back and more over time.