Property is an organizational structure in MyWordPress.io that allows you to organize your reseller account objects and client objects (sites, zones, etc.) into a logical grouping.
Most often, you first create a Property that represents your Reseller company and it’s associated sites & domains.
Once that is done, you then create other Properties that represent your clients, with their own site & domain settings.
You can also use Vanity Nameservers for your client domains that point back to your reseller domain.