Some of you may know that Boone and Arcade can't be recruited if you're reputation with the Legion is 'accepted' or better. I simple wore NCR faction armour to get the option to have them join.
Raul can be found at Black Mountain during the quest "Crazy, crazy, crazy"
Lily can be found in Jacobstown during the quest "Guess who i saw today"
Rex resides at the King's HQ in Freeside after completing GI Blues
Cass is at the Mojave Outpost, she can be recruited after completing simple quests for the crimson caravan company.
Boone can be found at the top of the dinosaur in Novac at night, you need to complete his side mission "One for my baby" by revealing a certain someone as the culprit with the bill of sale.
Veronica at the 188 Trading Post if you're not vilified by the Brotherhood of Steel
Arcade at the Old Mormon Fort in Freeside
Last but not least, EDI can be found at the Mojave Express in Primm, all you need is a repair skill of 65, or a science skill of 55, or various pieces or scraps and electronics.
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