My thoughts, since you've asked...
So how does one identify a legitimate offer??
For starters, if you are
selling a timeshare, there is simply no scenario on Planet Earth in which you would be
paying money to your buyer or their "broker" (let alone in amounts of thousands of dollars) to do so.

That's illogical and just plain
nuts. Buyers
pay money, sellers
receive money --- pretty straightforward.
It should be a negotiable matter (...except with eBay mega sellers, who dictate and railroad buyers into mandatory use of
their chosen closer and terms, even though the buyer is the one
paying the closing costs), as to who selects the closer and who pays closing costs in a private timeshare resale transaction. Sometimes it's the buyer, sometimes the seller, sometimes closing costs are "split". What should
never be negotiable is the selection and use of
only either an independent, established and respected closing company (...or a mutually acceptable attorney) to handle any and all escrow and later disbursement of any
substantial funds involved. For small change or no money transactions, "escrow" is irrelevant.
For me, there are only a
very few closing companies I choose to
ever utilize, whether I'm the buyer or the seller and
regardless of who is paying. They include JRA Services and Timeshare Transfer (with no "s" after Transfer); both are located in Florida and both have a long (a decade or longer) and well established track record of competency, honesty and reliability. Into that same category, I would also include PCS Holdings. Most others, well...not so much. Far too many bozos and incompetents masquerade as "closing companies".
Scammers are almost always easily "smoked out" with some thought, examination and inquiry. They generally manage to exude a certain sketchy "aroma" and lack of knowledge in their communications. There is usually a song and dance routine creating unnecessary and entirely avoidable complications (Judy's gig of I'll "send you a (bogus) big check and you then send me a (legitimate) check for a slightly smaller amount is actually among the most common of red flags). Offers to purchase for more money than you are asking in the first place is always a dead "giveaway" too. Really now, think about it for a moment; who would ever
do that?
Convoluted stories creating time delays (to receive and cash your legitimate check and then just disappear) are common too (e.g. "My sister has just been abducted by marauding rebels and I now must go to rescue her, so I'll be travelling for the next six weeks"

). Elusive "judy" was allegedly "travelling for ear surgery", or some such nonsense. Most scammers outside of the U.S. avoid providing legitimate (or traceable) phone numbers, or having
any telephone conversations in which flawed or heavily accented English or their obvious larcenous intent might be inadvertently revealed. U.S. scammers, on the other hand, seem to actually
prefer to "work the phones", in an effort to use "charm, guile and persuasion" and try to fabricate a "rapport" and build a (completely unfounded, btw) level of trust before actually applying the "sting".
In my experience, sincere buyers and sellers fully identify themselves to one another and /or to the closing entity at some point and certainly
before any significant money is put on the table. A valid, legitimate transaction is
not a unilateral arrangement where the buyer stays in anonymous "cyber-hiding" (like "Judy", with a "hotmail" email address, no physical location or street address --- and using a "spoofed" or VOIP (or just non-existent) phone number. All these factors collectively make alarm bells go off promptly and loudly.
In short, there are almost always significant and
multiple "clues" that scammers inadvertently reveal.
They might think they are pretty smart. Unfortunately for them, TUGGERS are smarter. Some on TUG may even have many years of criminal investigation experience and are very familair with fraudster practices.
That's just a personal theory, of course...
