That is what puts me off, suggests the owner has no clue how to maintain a boat if he thinks that will make his boat look maintained. It does not matter how old the boat is, in some respects. The current vendor could have bought to sell on or possibly is not owner. Most people have receipts for diesel, servicing, repairs, mooring if its afloat, a licence if its afloat, BSC if its afloat, insurance certificate, etc etc. If in doubt probably best to have it surveyed and get a bill of sale. Use Gmail to confirm conversations. You may lose the boat, because someone who comes along and asks no questions may look more attractive.