Cheapest trip from Canada to anywhere for visa purposes

I'll be looking to base myself in Vancouver soon. In the past, you've always had to prove at the border that you'll be leaving again, one way or another. Last time they didn't take the "I'm planning on winging it" comment well, so fortunately I had a bus ticket to Seattle as well (from Vancouver).

This time I'll have a return airline ticket, so that's easy, but I know other friends who just want the cheapest form of a ticket out of the country. Last time I had a $22 bus ticket from Vancouver to Seattle. Is there a cheaper ticket that would serve this purpose? Every dollar counts when you backpack ;)

Note - it doesn't have to be from Vancouver. Anywhere in Canada, to anywhere outside of Canada is acceptable.

Best Answer

Considering that the cheapest way across would probably be walking there are many crossings that you can do this at:

Niagara Falls Rainbow Bridge

In Vancouver you can do this across the Peace Arch

You can 100% cross by foot into Lubek, ME, the only problem is I have no idea how to get to the Canadian side of the border through Canada as there didn't seem to be any land connection.

Next Cheapest would be the BUS

Greyhound: Montreal to Plattsburgh, NY fare is about $20 one way.

There is Windsor Transit to Detroit but as BrendanMcK pointed out it has to be bought on the spot listed fare is $4.

Vancouver to Seattle you already know.

Finally got onto Megabus. Depending on the day the one way ticket is $17-$21 one way.

One more thing that may be a possibility but I have no and can find no information on hitching a ride with a trucker going from Canada to the US but I know that there are a lot of those going from Montreal and Toronto.