you need a margin account.

You need a margin account even if you don't borrow money from them. At the beginning, I had only cash account too, but I changed to a margin account. One example:
Assume you sell some stocks on Monday, then
you can use the money immediately to buy other stocks if you have margin account.
But you will have to wait until Thursday to use the money if you have a cash account.
That's mean that, with a margin account you can use your money much more efficiently so that you won't miss the chances (to gain or lose.

If you trade frequently, with a margin account you can use you money many times a day, But with a cash account you can only use your money once for every 3 days.

So my brother, go to get a margin account BUT DO NOT borrow money from them!