An existing business has a track record.  The failure rate in small business is largely in the start-up phase.  The existing business has demonstrated that there is a need for that product or service in a particular locale.  Financial records are available along with other information on the business.  Most Sellers will stay and train a new Owner and most will also supply financing.  These last two are important considerations.  Finding someone who will teach you the intricacies of running a business and who is also willing to finance the sale can make all of the difference.