You pay fees, but in exchange you receive a complete system to operate the business successfully so you don't have to waste time and money guessing about what you should be doing in order to be successful.
The disadvantage of buying a good franchise is that there are going to be lots and lots of rules about how you need to run your business and you will be expected to follow these rules without exception.
If you are a true "fly by the seat of your pants" entrepreneur, this can be frustrating or restricting. Therefore the trade off is between more fees, structure and security versus more freedom and risk of your investment.
The real key to success is that you need to find a good franchise and they are not all good. The secret is that you'll need to do extensive research and talk to lots of existing franchisees so that you can verify a proven track record that shows that a new person like you can enter the system and follow the rules and have a very high probability of being successful.
If you can't verify that exact fact, look for a different franchise to buy.