Have a look at this median house price map. It will show you the cheaper suburbs closest to the cbd.
http://reiv.com.au/Property-Research/Median-Prices/House-price-maps
Footscray used to be the 'scummy' suburb, but it's recently had a big surge in price and young professionals moving in. While it could be a good move, it could also be that you've missed the latest boom in that suburb? (p.s. I'm no expert).