Check out this great article in the ST about combining adjoining condos.  This is clearly not for the low-involvement, short-term investor but then again, those folks no longer exist.

Watermark condo

When Dave Roberts got a chance to buy the adjoining condo to his in downtown Seattle's Watermark Tower, he jumped at it. The result is a long, clean-lined home with views all around. Architect Tyler Engle started at the entry with a brazilian-cherry wall that invites you into the living area while hiding a bathroom and offering storage space. 

Full article on ST here.