As a first time rottie owner, I can tell you this is going to be ALOT of work. They NEED training, they need lots of attention, they need a tall fence. 6 ft is a good option, I put in a 6ft privacy just for my dog. They are strong willed, they will learn who they can push around, and will do so if not trained from the START.
I'd borrow, or buy a copy of "rottweilers for dummies" as they give a good detailed explanation of what it takes to own/raise one of these guys/gals. Here is a sight that will help tell if this dog is right for you or if maybe another home would be a better option for this dog.
So you want to buy a Rottweiler