Can I have help awarding money to a player for every kill?

This depends on how the weapons are scripted, but in most weapons, there is code to add a 'creator' tag to the Humanoid that the weapon is damaging. So to detect who killed what alien, you'd probably have something like this.

local Players = Game:GetService("Players")

function AlienKilled(alien, killer)
    print(killer.Name .. " killed an alien.")
    -- award points to `killer`
end

function AlienDied(alien)
    local tag = alien:FindFirstChild("Humanoid"):FindFirstChild("creator")
    if tag and tag.Value then
        AlienKilled(alien, tag.Value)
    end
end

function AlienSpawned(alien)
    alien:WaitForChild("Humanoid").Died:connect(function()
        AlienDied(alien)
    end)
end

Workspace.ChildAdded:connect(function(child)
    if child:IsA("Model") and child.Name:lower() == "alien" then
        AlienSpawned(child)
    end
end)