I am looking at getting TeamCity for our CI needs and I want to understand which version do I need. Currently, there is a free version (the Professional Server License) and one that costs money (the Enterprise Server License). The Professional Server License works for up to 20 build configurations. We are a .Net shop and develop in Visual Studio 2013. I need to understand what goes in a build configuration. Is it a VS2013 solution, with all projects that are inside or each project in the solution will have to have its own build configuration? Our systems tend to have a lot of services that control all kinds of low level devices, plus Windows Forms/WPF GUIs and Web Applications, so one single solution tends to have more than 20 projects inside. If each project within the solution needs its own build configuration, then we need to pay for the Enterprise Server License. However, if the entire solution will be added under TeamCity as a single build configuration, that means the Professional Server License will be enough for the time being, until we reach 20 build configurations.