Fair warning, a full scale game will take A LOT of time and effort. Youre gonna need to really commit to this if you dont want to end up with vaporware.
That said, its definitely doable if you put in the time and effort needed to pull it off.
How many are you? What are your competencies? The most efficient way to go about undertaking a big project is to specialize in a specific aspect of development (animation, 3D modeling/art, programming, level design, sound). If youre all starting from scratch, this is also the best approach to learning the requisite basics for each discipline within a reasonable timeframe.
As for a specific timeline for development, that depends on where most of your talents lie. The idea is to show off a demo that will attract the talent you lack. If youre mostly programmers, focus on getting a functional gameplay prototype out the door. If youre mostly artists focus on getting something like a cinematic trailer done to show of the general artistic direction you want to pursue.
Basically divide the work into smaller more bite sized chunks. Its a great motivator seeing slow and sure progress with focused and directed effort. Get a single playable area working. Rig one character to completion. Make one enemy with functioning AI the character can fight. Get basic gamplay elements implemented (inventory, combat, UI). Small measurable steps like that which gives the team a sense of accomplishment and encourages you all to push on.
Basically, do not under estimate the power of having a plan.