Can a plaintiff ask a defendant about their assets before they win a judgment?

Not normally, and the reason is because the defendant’s financial affairs only relates to the collectability on a judgment and usually has nothing to do with the merits of a case. But there are exceptions – as in fraudulent transfer cases where the movement of assets is the heart of the case. Another instance where it is permitted is when the plaintiff is suing for punitive damages. Then the defendant’s net worth is relevant to the amount that would be considered appropriately punitive.