One unavoidable cost of converting to over to a VOIP phone system -- especially a PBX phone system -- is the cost of hardware. You'll need to have a data network extended to every desktop. And you'll need to have PBX-capable phones that are also VOIP-friendly. Often, you can use your current phones with special adapters. But if you have to lay out cash for new VOIP phones in advance, start-up costs can grow in a hurry. One way to ease these costs is to look for a provider that offers either free, or deeply discounted, phones with a new service contract.