Run for the hills! We've seen this show before.
If your TS had the kind of value that would interest a legitimate buyer, they would handle it like a normal R/E transaction and take their commission from the proceeds of the sale, not up-front. They wouldn't be making cold-calls to owners who've have not shown any interest in selling -- typically done by the owner taking some initiative to determine it's resale value and contacting a legitimate agent or internet sales-service (like here on TUG).
The sad fact is that these peep are _not_ licensed R/E brokers, they are scam artists, who prey upon the naive and unsuspecting. When they get your $$, suddenly their mysterious buyer will back-out but they'll "look" for another (they only promised to "market" your TS), and then become impossible to contact. They may have you sign a power-of-attorney or deed-in-blank to make you think it's going to happen. Then, you will own a TS with a clouded title, and $4000 less in the bank.
As another poster said, to see the true value of your TS (what they are selling for), do some research of your own. Check redweek.com and closed-auctions on e-bay. Legitimate sales are made from those who've listed a TS for sale is how it's done, not by making cold-calls to those who haven't.
Contact your state's Attorney General's Consumer Fraud Department -- look for their website.
They will likely have a team of attorneys dedicated to rooting out this sort of fraud.
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