So i am a 3d artist, i have enough experience to model game ready assets and rigging and animating them(in blender btw). Now that i want to get into unreal, i dunno where to start. Apart from learning the basics from youtube, can someone give a brief idea of the things to do to develop a multiplayer 3d game? plus how much time will it take to do the same(assuming that i have 3 hours a day)
It is all very dependent on the type, size and scope of the game you wish to create.
Share some idea of what you’re thinking of, and perhaps someone with experience in that type of game can chime in 
Not trying to put you down, I suggest you should start from smaller scale game to understanding the game engine instead of jumping to straight multiplayer game, even the a small multiplayer game request few people to create it from zero.
as mention above, if you are making a MMO RPG, you might need more then 50 people just about the content and the programming part.
I’d say around 2-3 years to make a full game. A demo/vertical slice with limited level design/characters/skills etc can be done in couple of months.
You can start from checking this 3 tutorials - “Multiplayer Souls-like action RPG”, “Multiplayer FPS shooter” and “Multiplayer dungeon crawler” DevAddict's Unreal Engine Courses
PS. They cover only gameplay side, so you will still have to figure out how to setup and run servers, handle users, save their data and such sings on your own.