-And they wouldn't complain if you used it 100% 24/7?
-And you are guarantied to always have 100Mbit available?
-And you are allowed to use the line for whatever you want, including reselling?
We share the line between 238 apartments. Which works out to less $10, for what is effectively almost always 100/100Mbit (I bet your line is also oversubscribed at your internet provider). So actually, our cost is 1/4 of yours :).
I am not GP but I am familiar with his ISP (or similar, I don't know exactly what ISP he has, although I can guess). To answer your questions in order:
No (It says that "overuse" is not allowed in the terms, but I have never heard that clause being enacted)
No (But it in practice you have 100/100 available at all times from at least local service providers)
No you cannot resell the line.