I'd wish I'd known how bad my husband was with money. He used to lose bills, and then end up not paying them, and we got into real trouble before I took over things.
My girlfriend married a guy who was deep in credit card debt, and didn't even know how much he owed. He lived with a brother and sister, and used to just hand over his check to the household 'pool', with no idea of what he was spending or how much was being paid on his debt. They are working to get it paid off, but they are really struggling, and it was not what she signed up for when she said "I do".