Buyer wants copy of passport?

I’d tell him/her to send me all the money first!
 Then I’d send him the item. 
But, no Passport!!!

The OP stated on the 16th he will not go the passport route.

More than likely you dealing with a criminal that is tied into a ID Black Market network. These networks are around the country and in Mexico, South America and Europe. These networks are run and controlled by illegal immigrants. They have scouts that hunt down ID cards such as State driver licenses, which they sell to the networks for $350.00 which is the average going rate. The big prize for the scouts is getting their hands on a U.S. Passport which sells for $1000.00 a pop. They send these type of ID's to their relatives out of the country who slightly alter the ID's by switching out the photos, using high tech digital photo gear that is state of art to modify the ID documents, so you can't tell them from the real thing. For example, an illegal immigrant with a New York U.S. passport can come into New York City, disguised as an American, wearing a Yankees cap and jacket pretending he was out of the country for a brief time and he walks right in and disappears into the jungle. This has been an ongoing problem for Homeland Security during the past 10+ years.

be sure and send him you SS number......

Same experience here. Someone saw my ads on markt de and requested me to send the picture of serial number, the next day, the picture of the product in close up, the next day again, the video of the equipment when playing and finally, my picture with the product at the background. The next day, he disappeared without a trace.