Same end result, the money doesn't come from the gross though. Well, it does indirectly cos the studio has to get the money from somewhere, but their contracts usually aren't written in such a manner as they directly get the gross percentage straight to their bank account like a movie actor would (if movies ever actually made any money on the books). Which is all rather simplified, but I think it illustrates what I mean.

As for the contract length, yes the standard sign on time is 5yrs, but those contracts are renegotiated at the end of every season. There is a term for the conditions kicking in I referred to earlier but I've forgotten it and my google fu is failing me. Not every actors contract has them, but many do. To follow the friends example, kinda a moo point though, the point is that they get screwed if the studio can get away with it.