I usually refer the client to an auctioneer or two that I am familiar with, then allow the seller to interview and choose the one they prefer, then assist them with the advertising and with anything they need the day of the auction. Afterall the Realtor typically keeps it listed up until the auction and can sell it before the auction. However every Realtor and auctioneer are different and may have their own customs and preferences. An auction has its own contractual agreements, and I assist my client from the beginning to make sure they understand the process and what they are doing and make sure it is in their best interest.

That is going to vary a little from state to state and will depend on your prior agreement. Unless you agreed prior to what your expenses are then that is probably up in the air. What is common and customary is going to change from state to state. If I myself as an agent were representing my client I would execute my fiduciary duties to the client and work in his best interests. I myself would present the options of the auction and give my client 3 or more reputable companies to conduct the auction. I would also sit in on the presentations and help clarify to my client what should be most beneficial to him. I would have done a market analysis beforehand and probably have recommended an appraisal to help my client determine the minimum bid on the home. Personally beforehand I would have sat down with him and determined how to advertise the auction and would probably bear some or all of the marketing portion of the auction. If the auction has already happened and there was no agreement on cost sharing before hand or if you feel that the agreement was not honored contact his broker and try to work it out. If that doesn't work out see if there was a mediation clause in your agreement and request mediation. Worst case scenario for all parties and the last option (in my opinion) would be to contact your local states real estate regulatory entity and see if filing a complaint would be feasible. Try to find that entity on the web and determine what rules and regulations are in contention and if a written complaint would be beneficial.