I'm building a tycoon. Currently someone can purchase as many tycoons as they want?

Hey guys,

I'm making a homeowners tycoon. Basically, someone is supposed to join the server, pick a house, touch a mailbox, and own the home. Everything works fine, however, when someone already owns a home, they are able to buy another one. This could mean that someone is able to join the server and 'own' every home before anyone even gets to them. I'm not sure how to script this.

The script I'm using for the mailbox is this:

name = script.Parent
owner = name.Parent.OwnerName

while true do
if owner.Value ~= "" then
name.Name = "Homeowner : " .. owner.Value
else
name.Name = "Nobody Lives Here"
end
wait(2)
end

The script I'm using for the ownership is this:

local ting = 0 --debouncer
owner = script.Parent.Parent.Parent.OwnerName
function onTouched(hit)
    if ting == 0 then --debounce check
    ting = 1 --activate debounce
    local check = hit.Parent:FindFirstChild("Humanoid")
        if check ~= nil then --If a human is found, then
            script.Parent.NewHouse:play()
            wait(1)
            script.Parent.NewHouse:remove()
            local thisplr = game.Players:findFirstChild(hit.Parent.Name)
            if (thisplr~=nil) then
                local ownstyc = thisplr:findFirstChild("Tycoon")
                if (ownstyc~=nil) then
                    if ownstyc.Value == 0 then
                        ownstyc.Value = 1
                        owner.Value = thisplr.Name
                        local message = Instance.new("Message")
                        message.Text = "You NOW own #1"
                        message.Parent = thisplr
                        wait(0.5)
                        message:remove()
                        script.Parent.Parent.Name = ""
                        script.Parent.CanCollide = false
                    elseif ownstyc.Value == 1 then
                        local message = Instance.new("Message")
                        message.Text = "You ALREADY own #2"
                        message.Parent = thisplr
                        wait(0.5)
                        message:remove()
                    end
                end
            end
        end
    ting = 0 --remove debounce
    end
end