Indie game storeFree gamesFun gamesHorror games
Game developmentAssetsComics

I know that this is over 50 days ago, but how much time and money do you think it would take to make multiplayer be possible?

I can't give an accurate number, as I haven't done a multiplayer game before, but suffice it to say that without the support of tens of thousands of paying players every month, I doubt it would be economically viable.