time? dirty rushing?

As a pledge, the time commitment varies wildly. Some fraternities do very quick initiations, others don't have you do much your first quarter but have u do a lot after you're initiated, while others will have you do a solid amount of work as a pledge and then the work load drops off a lot after you get initiated. It's a good question to ask at rush. After you're a full on initiated brother, the amout of time you devote to it is up to you entirely.
Dirty rush is any fraternity sponsored rush event that is not dry. So no alcohol basically. If I remeber right no girls at your booth either during rush week which is week 2. Also, you can't formally do any rush events before IFC info night which is the Sunday before week 2, which in the case for this Fall is Oct. 2. Hope that helped.