Does the employer support the green card, and how to ask

This is the question people are afraid to ask and later regret skipping. It is reasonable to ask, in writing, whether the company sponsors employment-based green cards, at what point after joining, and who pays the legal and filing costs. Policies vary widely, some start PERM at year one, some never do. Asking early is normal and protects you. How did you raise it without sounding demanding?