Hi...guys and girls

I have a few Q. about base building.
1. Is base Maintenance "off" or "on" on server?
2. How to repair walls and other stuff?
3. How much is Maintenance?
4. What happens if my floor disappears..will my safe fall to ground or stay in air?
5. What if I dont do Maintenance, will my base be gone for ever ?
Thx.