They explain all of those things here http://www.brickworld.us
Unless by "you" you meant me in which case I will certainly not be selling anything, just putting stuff on display.
Registering does not mean you're selling stuff, it means that you're putting up your lego stuff for people to see. However you can sell stuff, but you can only sell things, OR have things on display.
Oh well. I'm gonna have to go with displaying stoof. I wanna try and buy the cafe corner/green grocer just for the pieces so I can make my own building that attaches like that. Or I could take down my fire station and use those bricks. I already have the Cafe Corner, Green Grocer, and Fire Station already built too :V
But I need to get a baseplate or two so I could make something for that "5" theme.