When you get to know an area really well, you'll also be able to recognise that odd freak bargain property that comes up. Saw one in Blair Athol year ago that sold for $312k that by all intents and purposes was worth $350k probably rent for $330pw. A unit in Prospect that sold for $197k worth $230k easy, probably rent for $240pw. Even last week, saw a property in Elizabeth sell for $175k even though it should have gone for $200-210k - will rent out for $230pw, a 6.8% yield which is just about positively geared depending on what your IR is.
No development or construction needed and these certainly aren't regional/rural/mining towns.
Doesn't happen often and I can't really explain why it does at all, but when you know the areas you're looking at well, they do come up for whatever reason (desperate seller in many cases I imagine), and as only one buyer you should be able to get your fill.