You can use your own place or your rent space.
You can use a professional or you use someone who know how to assemble things in Wix
You can use a free hosting or a professional hosting.
The choice is yours.
Does your customer care? Do you care?
An example of business who switch from a WordPress site to a Wix site.
It attributes the post to http://saraelizabethgordo.wix.com/ who is the owner of the site. Seems the domain name is only masked.