No, Mac OS X is incredibly capable right out of the box.
With the regular Mac OS X (Leopard) you would be able to host multiple websites, act as a file server, have remote control, and run PHP, mySQL, etc. All of this can be done with no extra cost.
There are also a lot of third party applications under $20 that will help you set up mail servers, databases, TFTP servers, and just about anything else you’d want to do.
