You will first need a server machine. That means another PC on wich you will run the IRCD (the irc daemon/server). You will also need an "always-on" internet connection (like Cable). After you have all this you will need the program wich will run the actual irc server : look here for details about this subject http://www.undernet.org/forum/viewtopic.php?t=1584
The server should be running any flavour of linux that suits you best. So at least minimun linux knowledge is requiered. Setting up the server is not quite difficult, but getting the clients is almost impossible, considering the number of good networks that exist today, but nobody says you can't give it a shot
Good luck !
And to answer your question, nobody charges for irc servers, but the equipment you need doen't come cheap (especially the internet connection)
Well first of all you don't need no "flavour of linux" and no linux experience, and not even another PC, you can run a very smooth and nice IRC Server on windows, on your own computer, cause I don't think he intends to have more than a few friends connecting.
And I'm not sure what you mean by "nobody charges for irc servers" ..if you mean ..that you don't pay when you connect to one, then yes that's true, but if you were refering to the IRC Server software..well not all of it is free for example the IRCXpro software...not only that it is not free..but it costs up to 1000$...