Could anyone recommend a low cost hotel or B & B in Venice, Italy ?
You'll get more answers on the "Italy" section of this forum. Also a good idea to be clearer about what "low cost" means to you, in dollars or euros.
You might look into the Hotel Santa Lucia. It's a 2-star hotel near the train station. It's not near the major sites but the cost is lower. You can easily take the nearby vaporetto to the major sites.