My 13th is something I really want to be special...and it's allowed to be co-ed and stuff like that...but I have no clue what to do...I want us to be able to hang out..and i love to dance and I want to be able to at my party...but I can't rent anything cuz we're a little tight this year...any ideas?

just don't rent anything. Throw it in your basement. just make sure you have a snack table, some chairs, and a boom box (or sterio). And have fun. Be flexible, let the guests deside some stuff too. You don't have to dance the whole time, but you should dance a some of the time.
*have fun*