u could create the server on your own (by help of this page: http://wiki.bukkit.org/Setting_up_a_server ) i did it on my own as well, then just stop the server if u dont need it^^ so it wont make u additional costs when u host it on your computer (unless u want it to be running 24/7^^)
in case u wanna know, what ur IP is for friends to join: http://www.wieistmeineip.at/ (its a german page, but i guess u ll get the ip as well otherwise google it^^)