1. I dont know of any "cost data CD's" you should look into property objects. Do a forum search (Karl is the man)
2. If you want floor framing that can be used for take-off's the best bet is to use the beam tool, then create a schedule from the beam lengths. I set up all my pens, cross sectional sizes and the like in the favorites palette, Each for a different lumber size ie joists/bearers etc then create the layout with the correct sectional sizes and then create a basic schedule from there.
note: if you want to create the look of a floor frame in section, you can use a sneaky fill in a composite slab . Just two vertical lines at say 600mm centres for the joists. Then a 100mm composite under this with and empty fill for the bearer. This is very quick and effective but obviously you can't do a take off
3. Setting up layer combinations is the most effective way of representing new/existing and demo
4 dont know, probably not. I think it is in the wish list
Good luck