Yes it will bite you. If you have a multiplayer game, your Client will not be able to perform Gameplay related things without permission of the server.
So for example spawning, shooting, reloading, nearly everything needs to be replicated. You need RPCs for that, which run on the server. Clients will ask the server to do different things.
In my c++ project for example, my weapon class has double the amount of lines only because of all the replicated functions that i need to replicate reloading, animations, asking the server to perform the shot and damage etc.
If you want to make a multiplayer game, you will need to directly work on it.
If you are a beginner, i highly recommened to not create a multiplayer game as your first game.
But at last this is up to you (: