Originally posted by Ulthar:

these are great responses. I feel like it's 80% there - but it's the lack of story that will probably not appeal to my wife.

Are there any games that you would suggest that fit the bill?

Outward. Check that game out, it has everything you asked for except the building part. You can't build your own house, but you can buy/own multiple houses at a point in the game.

Both of you can start a new game and join each other worlds whenever you like and co-op thru the game. The only downside is, only the host gets quest rewards, but that shouldn't be a problem if you like the game coz you can just switch to the other players world and progress there, you can even pick a different story path on the new world and get different quest rewards too

You only need one copy of the game to play co-op locally or via the internet ( still split-screen). So you can both check the game out, and refund it if it's not your cup of tea