How to convince my dad for rats?

I have had rats before, and I absolutely LOVE them and I hate how they have one of the worst stereotypes in the world. But I love bringing my friends over and they couldnt get enough of my old rats! But when my last one died, my dad said no more rodents. :( Anyway, this is 2 years later. I am gonna turn 13 in November. I asked my dad if he would be willing to give me an early bday present, and he said maybe. So in a couple days, (when I get back to his house, I am in Texas at my moms house) I wanna tell him. Now, I know I could tell him that I am more responsible now that in a couple months I will be 13 and all, but just how? Any other things you would suggest for telling him? I REALLY REALLY REALLY want more rats, they are my 2nd favorite animal (horses first!) please help! and thank you for the people that give serious answers, it is highly appreciated!