[33girl]

There's no "set" number of women you need to start - that depends a lot on the size of the sororities at your school. Talk to Panhel and the Greek life office first. They will be able to let you know if there's any possibility of the campus coming open for expansion soon.

If, for example, out of the 5 sororities, only 2 of them are at campus total and the other 3 haven't made quota or total in years, your wish to form a new group probably will not be approved. But if all 5 sororities are at campus total and taking quota or close to it each formal rush and people are starting to complain the chapters are too big, it may be time for a new sorority.

No NPC group expressly "limits" themselves to a certain geographical area. Each colonization opportunity is assessed on a case by case basis.