Sam, Hi. I am a sophomore Sigma Kappa at Culver-Stockton College. I can try yo answer some of your questions, but the Greek system here is very unique, being on a very small campus.
1. Costs - Dues are not as bad as you might think, they can range anywhere from $25/m to $250/m. But everything that you pay goes towards helping the sorority, on your campus, and nationally. Some of the dues also go towards the house's philanthopy. (Sigma Kappa is the 3rd leading contributor to the Alzheimer's Foundation) A good thing to keep in mind, is that each sorority is different, and each campus is different. The bigger the campus, the higher the dues, usually.
2. Initiations - This varies from sorority to sorority. I can tell you that each house holds it's initiation ceremony very close to it's heart, and it embodies the spirit of the sororities.
3. Rushes (is that the same as initiations?)
No, they are two completely different things. Rush is a time when you get a chance to visit all the houses, and they show what they have to offer. If you decide to join a house, and they offer you a bid (While you are looking for a house where you would fit in, the sororities are also looking for girls who uphold their standards), you will go through a pledge period. That is where you pledge to become a member of the sorority, and you learn about the house, and basically make sure that you are willing to commit yourself to it, before the house gives you it's secrets.
4. The average number of people in one house
This again, varies from house to house, campus to campus. We have a campus-wide limit here of 70 members, but we are on a very small campus. Membership can range from 10 to 200 and up.... It all depends.
5. Opportunities - There are so many oppurtunities to get involved. It is so amazing and so much fun.
6. Pros - There are too many to list. It can be the most amazing experience of your life. You have a house full of girls who like you, and are there for you no mattter what. (It is a built in support system) You learn and grow from each other. It looks good on resumes after you graduate. It provides you with skills you can use in the future, a home away from home, and, most importantly, a lifetime of memories and friendships.
7. Cons - It is a large time commitment, and it isn't free, But the pro's outweigh the con's at least 10 to 1. .The other thing you might need to watch for when you're rushing is hazing... Ask if the house has an anti-hazing policy... the majority of the time, it will. BUT, also keep in mind that hazing is not as scary as it sounds, and just because a house doesn't have an anti-hazing policy, doesn't mean that they are going to beat their pledges or anything.
8. Sorority life - What can I say? It is a great experience, and it is awesome to have a ton of girls you can study with, party with, laugh with, cry with, and be able to call them your sisters.
9. Contact after graduation - I can't say anything about this for sure, since I havn't graduated yet, but I still keep very close contact with my sisters who graduated, and there are alumnae organizations all over. It never really ends, it just changes.
If you go thorough rush, make sure that the house you join really is waht you believe in and stand for. YOu shouldn't join a sorority just because your friends do. It is a big decision, and one that will impact your life forever. Sorry that I am so long-winded.