10,000 units of currency is the “notional value” of the trade, not the amount you must have in your account.
Retail forex is heavily leveraged, so that (in the U.S.) a broker may offer you UP TO 50:1 leverage. If this is the leverage offered by Forex.com, then the $10,000 position that you referred to will require $200 of your money in MARGIN. (This is 2% of the $10,000 notional value of your position, and corresponds to 50:1 leverage.)
In addition to the $200 margin required TO OPEN this position, you need to have enough money in your account to cover the risk you have decided to take in this trade. Let’s say your plan is to risk 30 pips (at $1 per pip). If your position is stopped out, you will lose $30. So, at least $230 must be in your account before you open this position, in order to cover the MARGIN plus your potential maximum loss.
When your position is closed (either for a profit or a loss), your $200 margin will be released back to you.
If trades requiring $200 margin are too rich for your blood, then you need to find a MICRO ACCOUNT, where the minimum trade size is 1,000 units of currency (instead of the 10,000 units specified by Forex.com).
The four common types of accounts available to retail customers are:
[ul]
[li]Nano accounts: minimum trade size 100 units of currency, margin (assuming 50:1 leverage) $2 per nano lot.
[/li]
[li]Micro accounts: minimum trade size 1,000 units of currency, margin (50:1 leverage) $20 per micro lot.
[/li]
[li]Mini accounts: minimum trade size 10,000 units of currency, margin (50:1 leverage) $200 per mini lot.
[/li]
[li]Standard accounts: minimum trade size 100,000 units of currency, margin (50:1 leverage) $2,000 per standard lot.
[/li][/ul]
There are some brokers (Oanda, and others) who allow you to trade ANY size position, including positions smaller than nano-size. That might be a good option for you.