To back up some, there's not problem day trading as far as required funds go: if you sell same day, the only affect on your account is the difference.
(eg With a completely empty settlement account, you can load up on $60,000 worth of ABC, sell it an hour later for $63,000, and three days later money shows up in your account. Comsec doesn't know there's no money in there unless they try to take some out).
The biggest problem with all of this is that if you get a trading halt (for example) while you're holding the bag - and if you're doing this stuff seriously then you have to bank on that happening some day - you need to pony up the cash. Do NOT do this unless you have that money. You could lose your house.
Also: Comsec really blows for this sort of thing. You've got rotten brokerage and abysmally slow order entry. If you can make the minimum requirements ($25,000), Interactive Brokers has half the brokerage, a much lower minimum charge ($6), and MUCH faster order entry (one-click if you want). Of course, you need have margin in your account, but seriously, if you don't have access to the money (or equivalent) you shouldn't be doing this anyway.
(If IB is too scary (and it IS scary), even Bell Direct is better than Comsec from a brokerage point of view).
...and if you are serious about day trading, have a good hard look at forex or index trading. Even better brokerage (and equivalents), no concerns about trading halts etc, vast liquidity (depending on what you pick), and all the charting stuff works just as well. You also have all the leverage you can eat.
PS: I should mention that Comsec is fine for longer term trading (though, do they still charge for conditionals? That's just dodgy, IMO...) - at longer time frames the brokerage hit isn't as significant. Day trading, though, is very quickly eaten up by that lil' critter. Work out how much movement you need just to make back the brokerage (in AND out, remember)... Now work out how you'd do with 0.06%.