Ketubot 102: Put It in Writing! Or Maybe Not

How do we each financial agreements? Do they need to be written down? Can we write them down? How can we prove their terms if they're not written? Plus, a prooftext for this discussion, apparently for both writing and speaking, from the "sharp ones," who make the condition of only providing for the wife's daughter as long as the couple stays together. Also, who should raise a daughter, the mother and her family or the father and his family? There's a story of a case that took place that illustrates the Gemara's approach here as an example of very dark self-interest.