This is a realy cheap bus company which is in the U.S and U.K, you have to book online with a credit card. so if your folks or a friend has a card you could use then pay them back...
http://www.megabus.com/us/
And then as for accomadation, just search the net for cheap backpackers in Minnesota, it will be cheap, don't be scared to sleap in a dorm room....