It depends on where you live, but usually, you first visit the place you want to rent. If you like it, you take arrangement with the landlord, sign a contract, and usually, you are now the tenant of...
That depends on where you live. In Az. the lease states that if any guest stays for over 5 days, he must add his/her name to the lease. Then it is up the landlord to either raise the rent or leave it...