I had a deal fall apart three days before closing because the buyer's lender suddenly decided they needed documentation for a $200 gift deposit from two years ago. Two years. The buyer's grandmother had given them money for their birthday, and now we needed a signed letter from an 87-year-old woman in assisted living confirming it wasn't a secret loan. We got the letter. Then they wanted bank statements from grandma. Then they wanted to know why the check was written for $200 and not a round number like $250. I don't know, maybe grandma thought $200 WAS a round number?? The seller had already scheduled movers. The buyer had given notice at their apartment. I spent four days playing detective trying to reconstruct the financial history of a birthday gift that wouldn't even cover a decent couch. The deal finally collapsed when the underwriter went on vacation and nobody else would touch the file. I now tell every single client to keep records of every dollar that enters their account, even if their kid sells a bicycle. Especially if their kid sells a bicycle.