The main advantage to buying an existing business is the saving on efforts, time and energy that must be expended to get a new business off the ground. Without the sleepless nights and start-up hiccups, you can spend the time to concentrate on making your business grow, earn and prosper.
By buying an existing business, you are also buying the customer base, goodwill and name recognition that comes with. A bonus with purchasing an existing business is that the return on your investment begins immediately. With a start-up, you must wait until your business is completely set up, promote the business before the customers start coming in and cash flow can begin.
On the down side, many existing businesses have higher purchasing costs, due to the fact that you are purchasing the successful (hopefully) business model in addition to the inventory, branding, previous advertising, and positive public opinion of the customer base.
A start-up, the success or failure of the business model is still unknowable, so the total price is usually less, although securing financial backing may be much harder.