There are many forums where Linux questions are answered for free, such as newsgroups and mailing lists. As a last resort, you can always use the source to track down and fix a problem yourself. Although support is available for Windows-NT, you should be prepared to spend as long as an hour on hold, with no guarantee that your problem will be resolved. Because of the closed source nature of Windows-NT, there is no informal, free support available, and bugs are fixed on Microsoft's schedule, not your's. Since Windows-NT is not updated frequently, you may wait years for bugs to be fixed.
All necessary documentation is included.
Support is available for free or for very low cost. There is no user licensing, so you can quickly bring additional computers online. This all adds up to a very low total cost of Ownership. Several companies offer commercial aggregations at a very low cost. Applications and Documentation is available for little or no cost.