I haven't gotten a chance to play with it yet, (wife keeps me busy), but check this out and tell me what you think.
http://www.gamefront.com/files/21519...nderground_rar
If that link doesn't work, try this one:
http://www.ducimus.net/skyrim/House_...nderground.rar
Player house I made in whiterun that i mentioned earlier. Fast travel to whiterun, look immediately to your right to the arch thats part of the city wall. You'll find a trapdoor in an alcove.