Answer:
I occur twice in eternity. And I'm always within sight.
A house where you are brought, If they find you or get caught. If you cross the government, This is where you will be sent.
What has ten letters and starts with gas?
What has one head, one foot, and four legs?
What always comes into the house through the keyhole?
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.