How can I fix my money data save?

I've had this problem in the past, all you will need to do is make the 0 into a -1, you're correct just a few lines of code.

scoreKey = "PlayerScore"

game.Players.PlayerAdded:connect(function(player)
    if player:WaitForDataReady() then
        -- create leaderboard
        local ls = Instance.new("IntValue")
        ls.Name = "leaderstats"
        ls.Parent = player

        --create the score stat
        local score = Instance.new("IntValue")
        score.Name = "Money"
        score.Parent = ls
        if player:LoadNumber(scoreKey) >= -1 then --If score is less than 0 then
          score.Value = 0 --Score will equal 0
        else --otherwise
          score.Value = player:LoadNumber(scoreKey) --It will equal the saved number.
       end
    end
end)

game.Players.PlayerRemoving:connect(function(player)
    if player:FindFirstChild("leaderstats") then
        if player.leaderstats.Money.Value == 0  then --If Money value equals 0 then
            player:SaveNumber(scoreKey, -1) --Save the money as -1
        else --Otherwise
            player:SaveNumber(scoreKey, player.leaderstats.Money.Value)   --Save it as you have it.
    end
end)

Hope this helps.