My parent agreed to purchase Realms server. A friend of mine created a Minecraft world and we have been playing that world for quite a while now. Since I'm on mobile, I cannot think of and find a way to download his world and turn it into my own Realm server. I had an idea and decided to create a dummy account with the Realm purchased so that he can have access to it and make it into a realm server. My only concern is that can my friend have access to my parent's bank account? When I press purchase Realm with that dummy account, one the payment methods include my parent's account and that's what I decide to use. Is it safe to do so?
Unless the payment information is saved to the device you purchase the Realms server on, it's safe. Minecraft will not save the payment information beyond the final four digits of the credit card, which isn't enough to purchase anything - they don't have any access to their bank account. The only thing your friend could do is not cancel the Realms server subscription.