Buildings (2)
Right now, all Blizzard will say is “We have some ideas like that on the table.” We should know more closer to launch.
When you start your garrison, you will have 4 buildings. They are the Town Hall, Mine, Farm & Fishing Shack.
Followers (3)
If you were liking the possibility that your Alliance toon can have a bunch of Orc slaves, I mean followers, you are out of luck. Sounds as though followers will all be from the same faction, although this could change.
Yes, there will be followers of other non player races (aka Arakkoa) for players to have in their Garrison (source)
Yes, you can name your followers whatever you’d like, assuming it follows Blizzard’s naming guidelines.
Getting started (3)
The Garrisons are available to level 90s when they upgrade to the Warlords of Draenor expansion. Blizzard has said they will be available “within an hour” of launch, which likely means there is an opening questline to do in order to start building your Garrison.
At this time, each character will have its own garrison, similar to how farms are unique to each character.
While alts can’t share a garrison with your main garrison, Blizzard has said there will be a way to make it easier to level an alt’s garrison.
Misc (1)
It sounds as though Garrisons will use both gold and a second unique currency (which can be seen on the screenshots) for purchasing.
Missions (1)
Mumper has confirmed that when you send your followers on raids that they can get not just transmog items but actual items from the current tier too. So hardcore raiders be warned! (Source)
Visitors to your Garrison (2)
No, unfortunately, your friends will have to be content to sit in their own not-as-cool garrison if you are offline.
Blizzard stated at Blizzcon that you can have a full 40-man raid visit your Garrison if you’d like. I can also imagine this will put a bit of pressure on Raid Leaders to have a wicked garrison, since you know fellow raiders will be checking it out 