The cost will be really expensive(its relative to how complex the game is) as you have to hire peoples such as:
-Network programmer
-3d modeller
-Rigger
-Game programmer
There are also alternative for example you can offer them a revenue share of your game which will be way more cheaper.
But If you dont have experience leading a team of game developer it will be super hard to start making a complex game like sims and with multiplayer feature in it since you will have a hard time figuring out how to hire people that are qualified
The first thing i would recommend is try to work on a small game first rather than a big game ,for example try to work with 1 programmer and you as the game designer to work on a simple game ,you can try to make a really simple game for example tic tac toe so you will get the experience as you move on to more complex project