Start buying your own groceries to get a sense of how much that costs while you’re still living where you are now. Become self-sufficient for food and eat only what you buy yourself. Explain to everyone else in the household what the experiment is and gain agreement that they won’t eat the things you label as yours. Start preparing meals so you have an idea of what you need in various instances. This will include things like spices that you otherwise might not have in mind. This will also help you budget travel expenses if you don’t drive.