100$ is enough to get profit and to start. but losing at 100$ many times is not good.. amount is not important to start in daytrading but lot of experience.. before entering in daytrading study will and practice before invest so even in small amount you can profit if you have a lot of experience...
$100 is very little amount for day trading but if anyone is a beginner he could practice trading with this amount. Also if anyone have less money like 100$ for trading, he /she should do the regular trading as it will be more profitable for him. Day trading is more risky.