Guess I was lucky. Got a B&S powered mini bike from neighbor for $25 when I was 10. Clutch springs were broke so I took some off my pitch-back, cut them shorter and bent the ends to make it work. I was real lucky not to lose a leg when they let go and the clutch shoes went flying at about 3,000 rpm. Next step was my mini enduro my father bought unexpectedly when he went to buy my older sister her first car. I can still remember every single second of that day. I never asked for the bike, but my father knew I wanted it. I mowed a lot of lawns to pay him back the $100 he spent for it (only got $5 or $10 a lawn back then). He never asked me to pay for it, but I was so stunned and happy he bought this for me, there was never any question I would pay him back.
And of course, riding was a whole lot easier in 1972 than it is today. Our small addition was surrounded by huge cow fields covered with trails everyone rode on every day. Cows didn't seem to mind. Now, those fields are covered by malls and houses.
But we used to walk or hitchike all over town when we were 14. No way would I let my kids do that today. There are a lot of things I did as a kid, that I wouldn't let my kids do now.
Your father may change his mind. He might not. Most parents realize that children go through stages: they want something so bad today and don't even think of it a few months later. It's not a cheap hobby. And it can be a dangerous hobby.
Be polite, respectful, hard working and hope for the best. Beyond that, you have no real control.