How can I get guinea pigs with parents who are split up ?

Hi everyone, I’ve been wanting guinea pigs for nearly 2 years, I’ve done research and know how expensive they can be due to vet bills and how delicate piggies can be!! I’m 16 and though I don’t have a job just yet I’m actively looking for one, preferably in the veterinary field as I’m hoping to become a vet nurse in the near future. I have enough savings to pay for toys, treats, fleece, veggies etc but not vet fees just yet and I wouldn’t want to make my parents pay for the vet fees even though they can afford them. I’ve thought about becoming a foster for a local rescue so I can look after many guinea pigs and not have to worry about vet bills yet still be able to spoil many pigs as they deserve. My mom signed a contract saying no pets however (and doesn’t want any) and my dad isn’t too keen on getting pigs because he works full time and as the arrangement is that I live at my dad’s 50% of the time and mom’s 50% of the time I don’t know how to make it work. I know “if there’s a will there’s a way” and I am so determined to make it work. I just don’t know how. Any help is so appreciated, thanks.