If you’re looking to start a new business and have the crazy idea that you’d like to make money doing it, a list released by Forbes and the Raleigh-based private-company data provider Sageworks might be of interest to you. Based on information obtained from 100,000 privately-held companies, Forbes isolated the ten most and least profitable businesses currently out there.At the top of the heap:

Of the winners, little surprise that professional services - accounting, law, design and medical-related firms - accounted for eight of the top 10. Two big perks here: constant demand (no matter what the economy is doing, people will still get sick and still sue each other) and relatively low overhead. Bean counters trumped all, with a 25% average pretax margin. Next came the legal-service firms, at 21.6%, followed by dental offices (20.9%) and specialty design shops (17.6%).

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Those specializing in professional services - chiropractors, optometrists, therapists - were among the most profitable. On the other end of the scale were those businesses with low entry barriers, lots of competition and little or no control over either buyer or supplier pricing. We’re talking your support/services, small food manufacturers, trade/conference organizers and the like. And the ultimate winner, er, loser:

Take community care facilities, the worst of the bunch with a -7.2% average pretax margin. This sector includes residential care facilities that also offer nursing assistance or other health services. Not only is the overhead overbearing, there’s a shortage of nurses worldwide, pushing up wages. Pricing power is limited, too: In the United States, these facilities get paid by Medicare and Medicaid, a relatively stingy twosome.

It should be noted that this is merely a snapshot, and that many factors, including the value of the dollar, overall economy, and fuel costs, all affect the overall picture year in and year out. Still, it is certainly much food for thought as you get ready to start a new or different business with the bottom dollar as a top priority.