[HamletEagle]

I don't think there is a simple solution. Plugins can either use cs_set_ser_money(so you could hook Money message) or directly set m_iAccount with set_pdata_int. To detect the latter you will have to hook set_pdata_int with orpheu. Then you also need to check when the game updates the user's money, but this will likely be easier, as there are fewer places where it happens(buy menu, round bonuses, etc).
This approach isn't that great and doesn't account for 3rd party modules updating money.

Another way would be to try some kind of brute force approach. Hook something like PreThink or a thinking entity with a small think time and constantly check if the money amount was changed.