Our customers own the design and code. The email platform is Google Business Email and you’re correct, that’s 50 business cards, email services and website maintenance for $115/month.
Yes, it's a single account. Google charges $5 per user.
The risk of users using the service and cancelling was our initial worry. However, when a plan is cancelled, that includes the private domain, responsive website and secure hosting.
The user would need to find a way to reproduce the site, wait for the domain to be released and/or transferred, purchase hosting, then upload the site. We feel, if the user can handle doing that themselves, then they aren't our target audience anyway, right? And if they pay a freelancer to do it, odds are they will charge a large amount that will make the user have second thoughts. (We're hoping!)
Have you not found any risk in users using the service as a cheap design and build and then hosting the sites else where after?