[aephi alum]

When I was an undergrad, only two sororities had houses, and mine wasn't one of them.

The first sorority had quite a large house, so pretty much every non-freshman had to live there in order to keep it at capacity.

The second sorority got a smaller house. They had an interesting way of doing housing. Certain officers had to live in-house. They filled the other spots by offering them to the sisters - first the seniors, then the juniors, then the sophomores (freshmen weren't eligible to live in-house). They had a rule that if any spot in the house went unfilled, then all sisters who were eligible to live in-house but chose not to, had to split the cost of that empty spot. (AFAIK, they've never had to invoke this rule.) So no one, except for the President and a couple of other officers, was ever forced to live in-house.

My chapter now has a house, but I don't know what live-in requirements they've adopted.