You'll need to find a currency exchange, open an account, and buy BTC with your 10 USD. It's the same thing you'd need to do if you wanted to buy yen or euros.
http://www.mtgox.com is one such exchange.
http://www.mtgox.com is one such exchange.
No, it's not. I can go to pretty much any local bank and buy euros.
No, it's not. I can buy currency with cash, it will take me 10 min to get them from a local bank.
With bitcoins you have to jump through all kinds of hoops and pay all kinds of fees.
Now, what % of $20 would be gone by the time you get your bitcoins?