I've worked in timeshare law for a number of years and this is a very common scam. I had one client that ended up paying nearly $300,000 in fees (all part of the scam). I wrote an article on this subject a couple of years ago for my state bar. Here's the relevant part:

"Outright fraud is also common. Many timeshare owners have been contacted by a supposed timeshare reseller or escrow company and told that an individual or company seeks to purchase the owner’s timeshare, usually for an outlandish purchase price. Owners, thinking this is an answer to prayers, sign the sale contract, only to find shortly thereafter that a “foreign tax” is required to release the funds. Once the owner pays the tax (via untraceable wire transfer), any number of additional fees is then claimed to be required. Once the scammers have received hundreds to thousands of dollars, all communication stops and the owner is left with the timeshare."

I'm happy to answer any questions, but I'm glad I got on to see this because I've seen far too many people fall for these timeshare scams.