Is there a reputable company that will help a consumer sell an unwanted timeshare?

Has anyone successfully sold an unwanted timeshare property? If so, through what company? I am aware that there are a lot of companies that scam people out of money under the guise of trying to sell a timeshare, but is there a reputable company that can buy a timeshare from a timeshare owner? One that doesn’t require a payment up front to "place an ad" or "for closing costs?"