It is a motto of sorts which everyone on Xbox Live will be able to see if they look at your profile.
yes, you can play DLC that was downloaded on a Xbox LIVE profile and play it on a non Xbox LIVE profile
It will automatically ask you if you want to use your existing profile as your live account and just say yes.
You are not required to be on xbox live. Although you get a free month when you create a profile, it will expire. If you don't buy xbox live you will not be able to play online, be in xbox live partys, or get access to content on xbox live like game demos, add ons, videos, and music.
If the two profiles are different saves, they should indeed be able to work on a single profile.
yes.
You cant sell a Xbox live profile.
Yes, just select the profile and choose "Join Xbox Live." You may have to change your gamertag, but your Gamerscore will stay the same.
if you get a certain type of halo and join xbox live then yes
The number next to your profile is the number of years that profile has been on xbox live.
To get a Xbox live membership, you need to register. Your profile must have been registered to go online.
When you purchase Xbox LIVE, it is on your Xbox Profile. Therefor, any game you play (after redeeming the code or purchasing Gold Membership on the dashboard), you'll be able to play online.