There is no minimum deposit or minimum balance required to open an OANDA account for forex trading. You only need make sure to have enough equity to open positions of sizes you are comfortable with including margin requirements. You can calculate the margin required when you open a position in a currency pair using the OANDA Forex Margin Calculator .
The foreign exchange market may be left unregulated by governments, with EXCHANGE RATES between currencies being determined by the free interplay of the forces of demand and supply (see FLOATING EXCHANGE RATE SYSTEM), or they may be subjected to support buying and selling by countries' central banks in order to fix them at particular rates (see FIXED EXCHANGE RATE SYSTEM).
One unique aspect of this international market is that there is no central marketplace for foreign exchange. Rather, currency trading is conducted electronically over-the-counter (OTC), which means that all transactions occur via computer networks between traders around the world, rather than on one centralized exchange. The market is open 24 hours a day, five and a half days a week, and currencies are traded worldwide in the major financial centers of London, New York, Tokyo, Zurich, Frankfurt, Hong Kong, Singapore, Paris and Sydney - across almost every time zone. This means that when the trading day in the U.S. ends, the forex market begins anew in Tokyo and Hong Kong. As such, the forex market can be extremely active any time of the day, with price quotes changing constantly.