outcasts

1. There is:
Charon-karma?-Underworld
Jericho-bad karma-Megaton
Fawkes-good karma-after you get out of Ravenrock
Paladin Star-good karma-Citadel Lab
RL-3(Mister Gutsy Robot)-neutral karma-around RobCo factory
Thhese are the main followers.

2. If you're talking about the DLC it should be in your map, but if not then there is Fort Independence. It is west of Arlington by the Fairfax Ruins I think.

3.No you can't.

Another ollower is:-

Name=Clover
Location=Paradise Falls
Karma=BAD
How= Buy from Eulogy Jones in Paradise Falls for 1,000caps(500
with 50 barter)
Armor= Dirty Pr-War sping outfit
Weapons= Sawed Off Shotgun, Chinese Officers Sword

NOTES
-Sh can wear power armor
-Will NOT use weapons with lower damage than default weapons
-Loves using the SHISKABAB melee weapon

1) mamba answered

2) DC

3) no you sure can't but you can find one on top of DC's tallest building I think, but I know there is one around DC for sure.

1. There are eight followers. Two for Good Karma, Two for Neutral Karma, Two for Bad Karma, and two that can be taken regaurdless of Karma.
Bad Karma:
Clover - Paradise Falls. Talk to Eulogy Jones, and there should be a Karma option if you have Evil Karma. From there you can buy Clover off him for 1000 caps or so. Uses a sawn-off shotgun and a Chinese Officer's Sword.
Jerico - Megaton. He'll be walking around all day. If you have Bad Karma and 1000 caps to pay him, he'll join you. Uses a Nail Board and a Chinese Assault Rifle.
Neutral Karma:
Sergeant RL-3 - Found hanging around Tinker Joe. Tinker Joe normally hangs out around the Robo-Co factory, next to Tenpenny Tower. You can buy him for 1000 caps off of Tinker Joe if you have Neutral Karma. Uses an intergated plasma rifle and flamer.
Butch - Found in the Muddy Rudder bar after you complete the side-quest, "Trouble on the Homefront". Dunno if there's a special thing you have to do to get him to show up, but he should be hanging around the Muddy Rudder. He's free to join you if you have Neutral Karma, but he's considered to be the weakest of the partners (next to Dogmeat). Uses a 10mm pistol and unique switchblade called "Butch's Toothpick".
Good Karma:
Star Paladin Cross - The Citadel Lab, which becomes open after completin the Main Quest, "The Waters of Life". If you have Good Karma, she's free to join you. Uses a Super Sledge and a Laser Pistol.
Fawkes - Outside Raven Rock/Outside Underworld. You'll meet Fawkes in Vault 87 during the quest "Finding the Garden of Eden". If you don't help him escape from his chambers, you won't find him afterwards. If you do help him escape, not only will he get the GECK for you, but after the quest "The American Dream" he'll show up outside of Raven Rock with a Gatling Laser. If you have Good Karma, you can recruit him at this time. If not, you can find him hanging out outside of Underworld (Inside the building, outside of Underworld). Probably the strongest Follower. Uses the unique Super Sledge, Fawkes' Super Sledge, and a Gatling Laser with unlimited ammo.
Any Karma:
Dogmeat - Found in the scrapyard being attacked by Raiders. Recruitable no matter what your Karma is. Probably the weakest, as he has no ranged attacks, has weak melee attacks, okay HP, and often runs into situations that get him killed. Useful, however, as he can sniff out weapons, ammo, meds, and other things for you. No weapons other than Melee attacks.
Charon - Underworld in the Ninth Circle bar. Buy him from Azrulkoth. He costs 2000 caps, or 1000 if your barter is high enough. Or, talk to Azrulkoth and get a deal to kill Greta (another Underworld Resident). Either way, you'll recruit Charon. Uses a unique Combat Shotgun and a Combat Knife and is generally pretty tough.
There are also a few temporary followers like Sydney and Sticky, but I won't get into them right now.

2. Fort Independace, towards the southeast of the map, unless you're talking about the DLC, in which case it's east of the Citadel, shortly through a subway station. Then, follow the outcasts while fighting to their base.

3. Nope, the only one is in the armory at the end of Operation: Anchorage.