$8 buy/per transaction
$8 sell/per transaction
If you say "at the market" your trade will be the next in order on the floor after it is delivered (electronically)
at whatever price is in force at the time, after you hit the go button
or, you can type in any price you want, and also for how long you want it to be up and if you will accept
breaking the trade into smaller pieces, and when and if the price hits, your trade is exercised
after they get to know you, or if you have a big balance in account, you can buy on margin (borrowing a part
of owed amount), and yes you pay interest for as long as you keep it. Or you can pay full, no interest.
once you join up and get a password, its all self explanatory when you get to the trading page.