Have you researched the market for your potential business?
You need to find out as much as possible about other businesses in your area of work or geographical area to assess your likely chances of success - for instance:
Check out trade magazines, the business press and ask local enterprise agencies for their opinion.
Have you considered a franchise?
This is a way of setting up a supported business with backing - particularly for publicity and a brand name. You run your own entirely separate business, but you pay money towards the branding and central publicity. Your risk is reduced as the business idea is known to work - although there is no guarantee that it will work for you in your area. Well-known franchises include The Body Shop, McDonalds, Prontaprint and Dyno-Rod. See Information resources for links to Franchise Associations.
Remember that you must take professional advice before setting up your own business.