First of all you need a Team and a Licence from OWI (min 10 Admins and lot more)... price for a Server with 100 Player maby 70-115€ Per month. But honestly, that's a stillborn idea. You need admins but also an active community. If you're interested in the topic, find a favorite server and apply to be a trial mod there. First learn to be an in-game admin before you start running a server. You should have real server and programming knowledge for that, or you'll have to pay a lot for it.