I'm afraid that's just how the credit card payment processing system works. Buyers can always dispute charges and almost always win; when there's a dispute, the disputed amount is immediately removed from the account of the merchant and held in escrow until the dispute is resolved, which nearly always is in favor of the buyer. There are a few services that provide what amounts to chargeback insurance, but they are extremely costly and not generally worthwhile. Unfortunately, chargebacks are kind of a cost of doing business.
The only real protection, if you call it that, is our signed Rental Agreements. As a legally valid and binding contract, if the guest does not comply with the terms by paying you as agreed, you can sue them in small-claims court. In most cases, they won't appear in court and you'll win by default, whereupon you can take further legal action with the sheriff's office where they live to collect the debt. Not fun, and not fast, but it's possible.
