leaderstats is not a valid member of RBXScriptSignal. What do I do?

I'm trying to do a quest system and get 5 cash if I finish it

local frame1 = script.Parent
local frame = script.Parent.Parent.Frame
local talksound = script.Parent.Parent.TalkSound
local clicksound = script.Parent.Parent.ClickSound
local accept = script.Parent.Parent.Frame.Accept
local deny = script.Parent.Parent.Frame.Deny
local accept2 = script.Parent.Parent.Frame.Accept2
local deny2 = script.Parent.Parent.Frame.Deny2
local deny3 = script.Parent.Parent.Frame.Deny3
local player = game:GetService('Players').PlayerAdded

while (1) do
wait(1)
    if script.Parent.Value.Value == 5 then
player.leaderstats.Cash.Value = player.leaderstats.Cash.Value + 5
    wait(2)
    frame1:TweenPosition(UDim2.new(-1, 0,0, 0))
    wait(1)
deny3.Visible = true
        deny3.Active = true
        accept.Visible = false
    accept.Active = false
    accept2.Visible = false
    accept2.Active = false
    deny.Visible = false
    deny.Active = false
    deny2.Visible = false
    deny2.Active = false
    wait(1)
        UI.Visible = true
    frame:TweenPosition(UDim2.new(0, 0,0.85, 0))
    wait(0.5)
        local text = "Thanks so much!"
        for i = 1, #text do
            frame.TextLabel.Text = string.sub(text, 1, i)

            talksound:Play()
    wait(0.1)
    script.Parent.Value.Value = 0
           script.Parent.Parent.LocalScript.Disabled = false
    end
    end
    end

Normal script in ServerScriptService

game.Players.PlayerAdded:connect(function(plr)
 local stats = Instance.new("Folder", plr)
 stats.Name = "leaderstats" 

local cash = Instance.new("IntValue", stats)
cash.Name = "Cash"
end)