Congrats on deciding you want a horse. Did you know in some states of Australia you can get a job at 14? In NSW, NT, SA, TAS you can get a part time job at 14 if you have your parents permission and prove you are capable of working.
I'm not sure what discipline you ride, but in Australia you will pay a lot more for a fully trained youth western horse, than an english Pony Club horse. Because this would be your first horse, I'd assume you'd get a beginner's mount. You'd expect to pay anywhere from $2000 and up to $12,000.
I highly recommed you pick up a copy of HorseDeals from your newsagency and have a flick through it. It'll give you an idea of exactly what type of horse you want. Don't narrow it down to one breed or colour. You may have your heart set on a buckskin, but sometimes you just won't find one thats suitable.
This what I feed my boy and its average pricing. He gets lucernce chaff (about $30 a bag), oaten chaff (about $30 a bag), Mitavite Extra Cool (I think thats about $15 to $20 a bag), Groom (about $40 for an 8kg bucket), and Soya Meal (Not too sure of thats price.) Chaff normally lasts for me about 2 and a half to 3 months. Pellets last about 3 weeks. Groom lasts forever, and so does Soy. Feed prices vary depending on what you're feeding, and what season it is.
Before you even think of purchasing a horse make sure you have about $3000 to $10,000 in an account. Emergency equine surgery is not cheap! If anything ever goes wrong, it's good that you have that money to support you and your horse.
You can get some pretty cheap tack on Ebay. Sometimes second hand is alot better than those cheap synthectic ones. Goodwoods (Goodwood Saddlery
) has a great range of cheap saddles that are great if you're just starting out. In my honest opinion, I would just buy a good quality 2nd hand saddle.
Arr Vet bills. Everybody loves vets but hates the prices that come with them. In the city, vets charge a lot more in my opinion. In semi-rural areas, the prices are pretty **** good and in rural areas, they will charge more just because they have to travel more out there. My boy's teeth get floated twice a year ($130 each time) and he get's his shots done yearly ($110).
Now to the farrier. My boys gets his feet trimmed every 6 to 7 weeks as he is barefoot and only a yearling. I pay $33 for a trim and my Mum's horses are shod and that costs $85. Prices will vary according to where you live and what you want done.
If you want to show, then the prices go up even more. For most shows, you need to be registered with the appropriate breed or showing society. You also need to pay entry fees which can add up to quite a lot. You'll need to hire a stable, a camping spot etc. You'll need to have a float which costs quite a lot. My float as much as 3 of our horses purchasing prices combined.
Horses honestly do cost quite a lot, but are quite rewarding.