If you're going to be a day trader, you really need to know your stuff. It's risky, to say the least.
One of the most important elements to being successful is having access to very fast data streams so that you can make moves quickly as trends stat to develop in the markets. If you're planning on doing this using consumer-grade sites like eTrade, that's not a good idea. The web systems of many of the retail brokerage firms are not good enough to give you data fast enough for you to make good, timely decisions or to be able to execute trades way that day traders do in order to make their money. Many of those guys are living on very thin margins, sometimes just a few cents of movement one way or the other, so they make up for it with a large volume of trades.
One of the reasons you were told you need a big chunk of money to day trade is that some firms will rent you out a "desk" and computer access to day trade through their systems if you're really serious about it. They will require you to put up at least a minimum amount of money for this privilege, and $25k may not be too far out of the ballpark.