What do I say when he talks about moving out?

I'm sure he will bring it up. So far I've told him he can sleep in the spare room or downstairs. I'm starting school in Sept. which is going to be a big expense so financially it makes sense for him to stay. Also, it would be more difficult to show I'm GAL and doing 180s if he isn't here to see it.

What's the consensus about moving out vs separated living?