Even if we were willing to let it in, Had time to warm it, keep it very clean, (8–9)
Here's an interesting twist. In order for a dream to come true, you'd probably have to accept it—commit to the idea of it, make plans to realize it, and takes steps in your daily life toward it. It would take a big chunk of your time and resources (not unlike raising a child). What Brooks is getting at in this line is that some people, even if they really want to, don't necessarily have time or space to let a dream in.
Anticipate a message, let it begin? (10)
Looks like there's more to a dream than just doing, there's thinking and feeling, too. Not only would you need the time and space in your life to devote to your dream, you'd also need the mental and emotional space. That's tough stuff to come by when you're worrying about the zillion things you need to do and the family you need to take care of.
We wonder. But not well! not for a minute! (11)
Listen, people living in kitchenettes don't even have to time think about a dream, let alone go after one. As harsh as it may seem, their lives are dedicated to survival.