Changes

Venice offers a wide range of accommodations. Most of it is highly overprizedoverpriced.If you are trying to CouchSurf, it's nearly impossible in Venice itself - click the option "expand search within ... miles"

Camping Jolly. I wouldn't go as far as to recommend it, but you can rent beds in lockable tents there for less than 15 euros a night. Everything else there is highly overprized overpriced but there's a supermarket nearby and maybe you can ask to use the kitchen in one of the bungalows. Takes you 10-15 minutes to walk to the bus which brings you to the Piazzale Roma in 15 minutes.