Is it permissible to cease procreation until one's financial situation stabilizes, and is this considered birth control if there is no defined period for the financial situation to stabilize?

It is not permissible to stop procreation due to fear of poverty, because Allah is the Provider, and this resembles the actions of the Jahiliyyah (pre-Islamic era of ignorance), and it involves a negative presumption about Allah Almighty. However, if the cessation of procreation is temporary due to a health necessity for the woman, then there is no objection to it.