In a situation where one co-owner is buying out the other co-owner's interests in the real property that you are writng about, the attorney's fees incurred by the seller and their payment are typically subject to negotiation between the parties.Custom and practice in the real estate industry is that when a person sells his or her property through a real estate agent, the real estate commissions are typically paid by the seller. With that being said, an argument could be made that your sister has to pay her own attorney fees associated with the sale of her interest in the property to you.