What should I put into consideration toward this REO

Today see a crappy house, it catergrarized as inhabitated house right now, value only in land, which affered higher than exact land value though. Same floor plan and years old house in the exact same neighberhood offers at $460k, it is ask $300k.
The house definitely is not livable right now. Roof needs to be changes and reinstalled. All floor needs to be redone, the house seems been sitting ideal for quite a long time, it is mody, smily, yard is out of shape, however the main skeleton of the house is still fine.

Questions:

1. What is this inhabitable mean other than not livable? Any regualtions involved?
2. If seller stated the value in land, the house categrazied by county as inhabitable. Does this mean
buyer needs to get permit to repair the house?
3. How about property tax caculating? Is it true, the house property tax will be recaculated if the original
purchase is only for land?
4. Anyone can give a estamate how much will be to replace the roof, floor, redo the kitchen, electric circutry?

The house in san jose, ca

thanks very much in advanced!