All of the vendors are available at the Base of Operations except the Dark Zone vendors who can only be found in the dark zone safe rooms at the dark zone access points.
Most of the safe rooms around the city will have one or more of the regular vendors in them.
In the lobby of the Base of Operations. Sells Weapons applicable to your rank of different qualities. Will also buy all unwanted items.
In the lobby of the Base of Operations. Sells armour and wearable Gear applicable to your rank of different qualities. Will also buy all unwanted items.
In the lobby of the Base of Operations. Sells Weapon mods applicable to your rank of different qualities. Will also buy all unwanted items.
The Rewards claim vendor is found at the very back of the Base of Operations by following the corridor through the door that it almost immediately opposite the entrance. Walk past the stair to the Tech wing and continue to the back. This guy will have any items that you have eared through pre -order bonuses, owning other games or other promotional activity which the game may put out. If you have earned them, all the items are free and can be simply transferred to your inventory.
Available in the Tech wing of the Base of Operations after you complete the 'Armory' upgrade. This vendor sells a small selection of higher tier Weapons and gear. You can also sell items here.
Available at each of the Dark Zone safe rooms. (some entry points and locations inside the dark zone) These vendors sell specific dark zone guns and Gear and only accepts dark zone Credits as payment (earned from combat in the dark zone) Items for sale are only available if you are above specific dark zone ranks though (10 or higher).
Available after upgrading the supply line option in the Security Wing. This vendor sells cosmetic items for your Appearance, and skins for your Weapons.
Vendors requiring Phoenix Credits to buy items.
Available in the Base of Operations after reaching level 30. Find high end (gold) and superior (purple) items for sale in return for Phoenix Credits.
Found in the highest Dark Zone area (DZ06).