"Also, what do you think of the idea of containing the rain water from the roof. I was thinking I could use it for watering flowers or many other things."

Check your local regulations on that too, I know in Denver (and probably other parts of Colorado) that is illegal, once the drop hits something, it belongs to a water user, which is rarely the person who owns the land it falls on. Don't imagine it is enforced much, but I know 4 years ago it was because the drought was so bad.