Quote from bone:
The same way as the 47 States with balanced budget amendments - you do not spend any more money than you take in.
The States also have separate capital budgets.
It is not true that they only spend what they take in - they spend what they take in plus what they can afford to borrow. Picking a state at random - say, Maine - it has over $1B in state-incurred debt. Fully legally state incurred debt, fully compliant with the requirement that Maine's budget be "balanced".
It's really not all that different from what the federal gov't is doing, except that the debt ceiling is (more or less) formally tied to the ability to borrow, and the States can't print their own currency.