What do we need before a boy and a girl start a relationship?

I think to start a relationship the only thing you need is interest and curiosity about the other person. I think love and friendship come later on, and is what decides whether you stay with that person or not. However I think marriage involves way more than that even, you have to figure out if you are compatible in: family values, finances, religion, lifestyles, even things you don't really think about like food.