How does Minecraft Multiplayer work and how do I get it?

I'm getting the game really, really soon, and I promised that I'd keep in touch with Runescape friends after I quit. I'd like to have a personal server for just me and friends to use.

I'm hearing many different things, though. Some are telling me that I need to pay an incredibly high amount of money with recurring fee for a personal server, and others are telling me that I can make one for free.

Which one of these are right? And are there any interesting benefits to Multiplayer?

I think it's free if you run the server off your own comp.

Pretty sure it's paid if you use a server somewhere.

You have to have a good computer though.

If you want to host a server, you only have to download server tool from minecraft website, however if you want a server where it's probably lagless and hosts about 500 people or something you would have to get your own 'professional' server set up or buy one.