If you go to most Vietnamese bakeries at lunchtime you will see a queue of people ordering this cheap and cheerful food. It usually consists of a bread roll (often still warm), spread with some pate, then several varieties of cold pork, some tangy vegetables and finished off with coriander and pieces of fresh chilli. Healthy and satisfying - typical cost $2.20.
The best place to find shops selling good Vietnamese pork rolls are Footscray (Capital Bread Shop in Barkly Street opposite the Footscray Market), Richmond, Springvale Also in Smith Street Collinwood (SunnyT's Bakery at No.252 or N.Lee Bakery at No.220).
One word of warning - bad food handling (eg pate left in the sun) can render this sort of food a target for food poisoning, so choose shops that have a high turnover and appear clean. Having said that, it has never worried me. and if I get a craving I just head to the nearest store for a fix.