Up to four in split screen. We played it with my two kids in couch coop. We where three in split screen. Each player has one house. The money is shared, so I was working to get money, while my kids were exploring and having fun.

I don't remember exactly but one player is mandatory (the one starting the "save"/"world"), then the three others are optional. However you don't want to play a lot without the other characters since they will not progress (the more you do something with one character like cutting wood, the easier it is for this character).