Should I or Shouldn't I

I own a duplex next to me just because it's next door.One side is in need of a major redo.It measures about 24 wide by 22 long.I am trying to talk the wife into letting me make a man cave out of one side.I have it pretty well gutted.The way I have it now I could have a garage floor area of about 14 wide by 22 long with a raised floor area of 10 wide by 22 long.Sunken car area with raised play area.What do you think and how can I convince the wife to let me do this?One problem is I already have a 28 x 40 garage but it sure would be nice to have a cave like this.