You want to rent a game for your X-box. You want to make it when you want, even if you want, even if you want. When the Website Design agency completes all the functions on your website and the contract is completed, make sure that all files used on the website are proprietary. Really, put it in your contract. This will be easy if you choose to change your site anytime.
It is negative to say that like today, more than 1 billion websites have been released. And thus internet marketing is very competitive. Instead, the positive side is that there are billions of customers that are a great opportunity.