When you work with a genuine website design that cares about your growth you will get a specific set of features to ensure your satisfaction.
First off a serious website desigb firm will not hold any infornation from your website proprietary. Your website should be yours to own 100%. If you ever decide to leave that company, you should be able to take your website with you.
Secondly,  a good firm will offer to manage and maintain your website so you have the worry free experience you deserve for paying for a newly designed website.
Watch out for website companies who offer you a “free” website as everyone in this world should recogbize that nothing is free. Eventually these companies will begin charging you as high as 200$ a month to rent the website from them. The second you stop paying for the site chances are you will lose the website and all of the traffic that was going to it.
So it makes sense to deal with a company that gives you full ownership of your site. Anything that is strongly tied to your business needs to be owned by the business owner to maintain full control.