Federal Trade Commission has an excellent series deciphering some classic work-at-home schemes. The old saying still holds: if it is too good to be true, you'd better avoid it.

Envelope stuffing. Promoters usually advertise that, for a "small" fee, they will tell you how to earn money stuffing envelopes at home. Later - when it's too late - you find out that the promoter never had any employment to offer. Instead, for your fee, you're likely to get a letter telling you to place the same "envelope-stuffing" ad in newspapers or magazines, or to send the ad to friends and relatives. The only way you'll earn money is if people respond to your work-at-home ad.

Assembly or craft work. These programs often require you to invest hundreds of dollars in equipment or supplies. Or they require you to spend many hours producing goods for a company that has promised to buy them. For example, you might have to buy a sewing or sign-making machine from the company, or materials to make items like aprons, baby shoes or plastic signs. However, after you've purchased the supplies or equipment and performed the work, fraudulent operators don't pay you. In fact, many consumers have had companies refuse to pay for their work because it didn't meet "quality standards."

Unfortunately, no work is ever "up to standard," leaving workers with relatively expensive equipment and supplies - and no income. To sell their goods, these workers must find their own customers.