Interesting!
I'm actually right into setting up such a business in Sweden.
My idea is to offer "subscribtions" where the customer gets the server set up and running and also gets "unlimited support" (just for the server!!!) as long as the subscribtion continues.
I think this is a good way of getting on good terms with the customer and that should make it more easy to suggest/implement different "add-ons" on top of the already included services directly from the smeserver.
I honestly don't think I would manage to live just off the subscribtion fees, - but with let's say 20-25 customers it would be well possible.
I am also very interested in learning more from other people out there with similar ideas...