I disagree with the premise of the question. The economy should be fairly secondary when considering having children, unless we are talking about extreme cases. I see many people in developed countries who do not have children or postpone having them indefinitely because they have to go on trips to upload photos to Instagram. It is better to be clear about the unity of the couple, the common life project, and if you have limited resources, you will manage. That is how it has always been done. Another thing is that if you have limited resources, do not be foolish and have 10 children; take precautions.