Calling functions from other files

[Dead-VCR]

What would be the best way to call functions from other files? I have a money system in one file and I'd like to be able to access its functions and variables.

For example:

in one file I have this:
function titlestuff(ply)
    print(ply:Money_Get())
    if ( ply:Money_Get() > CUSTOMTITLE_PRICE ) then
        ply:Money_Take(CUSTOMTITLE_PRICE)
        print("yes")
        return true
    else
        print("not enough.")
        return false    
    end
end

Which calls the "Money_Get()" function (in a different file) as seen here:

local pm = FindMetaTable("Player")

function pm:Money_Get() -- player:Money_Add = GET THE MONEY FOR A PLAYER
        local current = tonumber(self:GetPData( "cash" )) -- Get the old amount of money
        return current
end

However, when I try to use that I get this error:
[ERROR] addons/title_store/lua/autorun/server/sv_titlestore_chatcom.lua:90: attempt to index a string value with bad key ('Money_Get' is not part of the string library)
  1. error - [C]:-1
   2. __index - lua/includes/extensions/string.lua:297
    3. titlestuff - addons/title_store/lua/autorun/server/sv_titlestore_chatcom.lua:90
     4. func - addons/title_store/lua/autorun/server/sv_titlestore_chatcom.lua:104
      5. unknown - lua/includes/extensions/net.lua:32

Thanks in advance for any help.

[SweptThrone]

what you're doing is fine, but wherever you're using titlestuff, you're passing a string, while the function expects a player.

[Dead-VCR]

That was it, thank you so much!
Another question before I close this;

I use this to send stuff from the client to the server:
net.Start("ts_shekelberg")
net.WriteString(clSelectPlayer:GetSelected())
net.WriteEntity(LocalPlayer())
net.WriteString(cltitleEntry:GetValue())
net.WriteString(cltitleAnimation:GetSelected())
net.WriteVector(Vector(clmixer:GetColor().r,clmixer:GetColor().g,clmixer:GetColor().b))
PrintTable(clmixer:GetColor())

net.SendToServer()

and it receives it like this:
net.Receive("ts_shekelberg", function(len,ply)
    local ply = net.ReadString()
    local pl = net.ReadEntity()
    print(pl)
    local result = titlestuff(pl)

    if (result == true) then
        for k,v in pairs(player.GetAll()) do
            if v:Nick() == ply then
                local steamid = v:SteamID64()
                player.GetBySteamID64(steamid):TitleStore_JSON_RemoveData()
                local text = net.ReadString()
                local anim = net.ReadString()
                local color = net.ReadVector()
                local saveTable = {id = steamid, title = text, animation = anim, color = color}
                player.GetBySteamID64(steamid):TitleStore_JSON_InsertData(saveTable)
                break   
            end
        end
    end
end)

how come "pl" is a null object? I've used "net.WriteEntity(LocalPlayer())" to send the player info to the server, why does it not work in this instance?

[LoweChaser]

Don't write local player, it's already in callback arguments (net.Receive("ts_shekelberg", function(len, ply))