I need help convincing my dad to help me buy a horse?

I'm currently out of a job but I'm desperately looking, I've got real little riding experience and living in a city were the board is 170p/w i know its ridiculous. but I've had three riding lessons and the instructor said i was a natural. I really want to go into Show jumping or Cross country so i can compete around Australia. i live in Western Australia. But i need help owning the horse, My dad is the only one who can help as my mum is short for money, I'm willing to do anything to own a horse, I'm responsible i own two birds and a dog and i love them all. i absolutely love horses and I've been told its best to learn to ride on your own horse someone you can make a partnership with. But my dad always laughs at me when i talk about owning a horse, now he does love me but his an *** and is really tight. he works in the mines and gets a lot of money. how can i convince him to help me own a horse