I'm finding the opposite. Of all the ads I've placed in the last 2 yrs, I've had almost no scammer contacts.

I always add the following:

Personal contact will be made via phone before any sale.

You should be able to tell within 10 seconds of conversation if you're talking to a genuine buyer or a scammer. Also, if the mention cashiers check, or use the words "my agent"......hang up.

Farmers don't work with "agents", whatever they are.