I live in a yuppie town where we have a Gucci dump (Called a transfer station.)
I have picked up a perfectly serviceable cast iron Singer straight stitch sewing machine for the taking. (The dump has a money-back guarantee policy too.)
While it is limited by the lack of a walking foot and zigzag, it will do most of the canvaswork you need that doesn't require those features.
As has been said, a lot of pretty nice, heavy duty machines can be had for very reasonable money if you spend some time looking.