Running servers

[Jes and guide dog Harley]

Hi all.
One of the reasons I want to run Linux is because I want to eventually be able to offer my own services to the outside world.
Services including mail, web, etc. I'm wondering if I should worry about what my ISP is going to think about this, or should I
even bother telling them at all. I'm afraid that if I do tell them they'll deactivate my account, which I think is obserd since
it's my computer and all they're doing is offering me my internet connection, so in my own mind, they should have no say, with
some exceptions, as to what I do with my internet. Obviously spam and other stuff they should have a say so, obviously don't send
it or we'll kick you off line. But as far as offering services and stuff, jeez. What's the big deal. Any thoughts?
Jes