Yes, you can in almost every state. If the renter doesn't pay their rent according to the terms of your rental contract, you can sell the contents one-by-one or everything together. Often storage unit owners will hold a public auction to sell the contents of storage units. Some websites are dedicated to helping people sell storage unit contents. Selling stored items is time consuming, but it is a way to recoup some of your loss. Information about what happens to storage unit contents if the contract is violated should be included in the contract.