Looking to create rpg that is online multiplayer with up to 4 or so other players. (new to Unity 3D)

First off, I want to say that I am brand new here. I have been wanting to design and create my own game for sometime and am finally deciding to give it a try working with a game engine. I downloaded Unity 3d tonight and it will be the first game engine I have fooled around with. I know and am aware there will be a small learning curve. I am not worried about that. What I was really wondering was this… My goal is to create a puzzle/ adventure/ survival RPG (most likely 2D) and have the players be able to play together via online coop with up to 4-6 others if they so choose. The game would be playable 1 player or by yourself. But in today’s world playing with a friend is always more fun. I know that this step is far off in the distance for me as I have not even started the project yet, but I wanted to find out more information on the online multiplayer end and if it is possible how I would accomplish this. Any insight and information on this would be greatly appreciated.

Oh, and I almost forgot, Merry Christmas all!!!

Im actually doing same, working on a mobile multiplayer Rpg framework, here is how I am doing things which seems to work well from my experience.

-All units have same base class Unit.cs which contain all the logic for stats calcul, animation control.
-i derive different unity from this base class so whenever i want to apply damage or buff i check my target if(Unit.IsMy) do logic
-this work for the singleplayer aswell. if i want to switch multiplayer i have a script common on players, enemies, npc “NetworkSync” which will synchronize movement/rotation and “actions” (animation trigger+sound+fx) like cast buff
So later adding AI over network would work out of the box
I am actually working on the skill system, I have a BaseAbility then i derive other class from it for example, if i want a skill that require a target and cast an Aoe debuff instantly on target i will use OnTarget_Direct_Aoe_Debuff but if i want a self heal on myself i will use OnSelf_Direct_Heal
you can check here more details:

http://forum.unity3d.com/threads/correctly-designing-a-networked-skill-system.286690/

Awesome! That will definitely come in handy once I get a better grasp on what I am doing here. I still am unclear about an answer to setting up online coop though.