Interviewing for j-o-b: when to ask about "we own you" non-competes?

I'm thinking of getting a day j-o-b while continuing to work on my startup on my own time.

I believe that some companies (like Google) write extremely restrictive employment agreements that basically say "we own everything you do while you are our employee." That wouldn't be a good match. Some others are more permissive: "just don't compete directly with us."

When is the proper time in the interview process to bring this up? In my hazy recollection of past jobs, this paperwork was offered to me only when I was about to sign my offer, which is rather late in the process.