But you can't do both at the same time. Good one-on-one consulting (or anything, for that matter) requires you to be 24/7 thinking of your client and their problems, not yours. Perhaps other guys are better at multi-tasking among completely different things. To me, you've got to pour your heart and soul into it, or it's not worth doing. That's just the OCD-kinda guy I am :)
My biggest problem isn't the savings, it's the team. I chose to live in a really rural area, which is great for kicking back after getting off a jet from somewhere, but really sucks wind when it comes to meeting and forming teams. I'm waiting for one of these YC groups to help us hermit schmucks out with some good team-formation software.
Apply to YC and let's hypothetically assume you get in.
Spend 20% of your time making this ridiculous amount of money you can make doing consulting, the rest on your startup.
Problem solved. =) In all seriousness though, didn't Xobni have to do something like this for a while? (side consulting)