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.

Medical billing. Ads for pre-packaged businesses - known as billing centers - are in newspapers, on television and on the Internet. If you respond, you'll get a sales pitch that may sound something like this: There's "a crisis" in the health care system, due partly to the overwhelming task of processing paper claims. The solution is electronic claim processing. Because only a small percentage of claims are transmitted electronically, the market for billing centers is wide open.

The promoter also may tell you that many doctors who process claims electronically want to "outsource" or contract out their billing services to save money. Promoters will promise that you can earn a substantial income working full or part time, providing services like billing, accounts receivable, electronic insurance claim processing and practice management to doctors and dentists. They also may assure you that no experience is required, that they will provide clients eager to buy your services or that their qualified salespeople will find clients for you.

The reality: you will have to sell. These promoters rarely provide experienced sales staff or contacts within the medical community.

The promoter will follow up by sending you materials that typically include a brochure, application, sample diskettes, a contract (licensing agreement), disclosure document, and in some cases, testimonial letters, videocassettes and reference lists. For your investment of $2,000 to $8,000, a promoter will promise software, training and technical support. And the company will encourage you to call its references. Make sure you get many names from which to chose. If only one or two names are given, they may be "shills" - people hired to give favorable testimonials. It's best to interview people in person, preferably where the business operates, to reduce your risk of being mislead by shills and also to get a better sense of how the business works.

Few consumers who purchase a medical billing business opportunity are able to find clients, start a business and generate revenues - let alone recover their investment and earn a substantial income. Competition in the medical billing market is fierce and revolves around a number of large and well-established firms.