We've covered this issue in past scam alerts dealing with title search fraud and Mexican timeshare fraud. However, repetition of ways consumers can avoid timeshare resale scams is always a good thing!
A title search only applies to deeded ownerships. Mexican timeshares are not sold as deeded property, they are simply a right to use leasehold. A title search does not apply to a Mexican timeshare sale!
For a deeded timeshare sale- the buyer wold have the option of purchasing a title search or a title insurance policy. This cost will vary by state, but is generally less than $300. In Florida- a timeshare title search from a respected title company or attorney should cost less than $100.
As a general rule, any timeshare reseller that requires the seller to pay any type of upfront fee has a very high potential to be some type of resale scam. Never pay any type of upfront fee to sell an unwanted timeshare week!