[WalterBright]

There's a classic one where one places a classified ad that says: "How to make money at home! Send XXX $10 for information."

Send them $10, and you get a letter that says: "Place a classified ad that says: How to make money at home! Send XXX $10 for information."

[jiscariot]

This was probably 30 years ago--make $100's "Stuffing envelopes."