Hi,
I would like to offer my take on this since I was in the same situation as you, a few months ago.
After talking to folks and getting feedback from an admissions consultant from Stacey Blackman consulting, I ended up choosing a different recommender (who was employed). It was tough for me as I was really counting on this recommendation. It was very difficult, but, I had a candid conversation explaining the circumstances to my recommender. He graciously agreed to inform me when his situation changed(which thankfully it did, soon enough!).
Much as one hates it, it becomes a perception issue. Schools perform background checks on recommenders. By having a recommender who is unemployed,you are risking this perception issue. Is it possible that one's recommendor gets laid off after submitting an appilcation? Certainly, this is possible. However, by eliminating risk factors, you are enhancing your chances of getting admitted.
I would suggest that you look at other recommenders, unless, you think that this recommender is worth the addittional risk.
-Stoic