I second the suggestion of getting a horsey person along with you if you respond to any classified ads.
If you google Brosha Park (just out of Bendigo) you'll get a really old website, but the contact details are current and you'll get an email response from the webform. They are training up a beautiful gelding called Trojan, who's 6yo. He's not proven, but he has a beautiful little temperament. At the moment you could get him for under $2000, but give them a call and see what you can work out if you want to go meet him, if you are willing to spend what you save on a good trainer to finish him off. I passed him over because my boy is not given to being sensitive and could easily make a pony like that a nervous wreck, so I went with another pony they had, who hadn't done as much and wasn't as 'pretty', who seemed more suited to DS - and she so is! Also, there's a stud called Mithril Welsh Ponies, in Kilmore that has a couple of fantastic little ponies for sale - one is Curlylocks, the other is Wiki. Same as with the Brosha ponies, you'd need to find a good trainer to finish them for riding. When I started looking I was shocked at how much I'd have to part with for a nice natured and trained pony - about $5k and then some! So, given my background (I finished breaking my own horse), I decided I could train a pony for DS to go on with and spend less if I got it now. To get a trained pony for NOW would have just broken us, so I'm a step ahead of where DS is at, training her myself and he rides at his own pace with her (they're both at the same level, anyway!) and rides the school pony on Saturdays. Does that make sense? There are good trainers around, just, again, go word-of-mouth Breeding is important with ponies, but it's not everything - the handling it receives is also going to affect its nature.
Otherwise, if you come across a Brosha pony or Mithril, rest assured it's had a great start to life and will be a good bet.
The Equiculture info is especially useful for small properties, so that's right up your alley - 3 acres, 300 acres, it's all doable, it's a matter of smart and diligent management. You may only have to supplement with hay if you investigate your grasses and play around with your fences, laneways and paddock set up. Horses don't need the pasture that's designed and marketed for cattle - all that sugar content is no good for horses and you end up with problems. Same with hay - most horses don't need lucerne. It's funny cos we feed horses, conventionally, the same way we did 150 years ago and use them soooo much differently from how we did then! Same with stable and paddock design - these things were designed when horses worked ALL day long EVERY day for our convenience, and stables are still built in this way, even when horses work infinitely less, even competition horses.
Anyway, some things for you to think about!