Average daily cost food and car rental

Hi everyone!

Since I know that there are no international ATMs on the islands, I was wondering how much money do I have to bring with me.

Is there anyone who can tell me, on average, how much food costs per day, both on São Tomé island and on Príncipe island?

Also, how much does it cost to rent a car per day? (Again on both islands) And whether it’s better to book it in advance or to rent it on the island at the moment.