Should we turn garage into living space?

My in-laws mentioned remodeling our two car garage to turn it into actual living space.  We don't actually park our cars in there and it'd be nice to have the extra room.  I'm thinking either a master suite or a den, laundry room, and extra bathroom.  I'm looking at DuraMax Stronglasting Teton Vinyl Sheds 20221 as extra storage for the bikes, tools, and miscellaneous junk that garages accumulate.

When my in-laws come into town, I am going to ask them how much it'd cost to do something like this.  It might be something we can plan for in the future as a project.  My mother-in-law says we have to do it before my father-in-law is too old to do it (he's going to be 81 I believe).