So, I have a portal type of website that I'm considering selling.
Let's for the sake of convenience, call my website www.portal.com. If I sell one of these portals, I would like them to be under the portal umbrella, and therefor have them as: client1.portal.com or if their company name is Microsoft, have it be microsoft.portal.com.
To add complexity, I would like there to be SSL on the website(s).
I'm assuming I need a wildcard SSL to facilitate all my clients as I don't want to change my certificate every time a client is added or removed.
The main question:
Is there a way that, for my client to keep their own website: www.client1.com, instead, redirect to client1.portal.com without them seeing this in their URL bar?
What do I need (incase I need to buy anything) and what is the technical term of achieving this?