How fast can I burn myself out???

So I'm still working for USPS Fri-Mon in the evening. I started tending my friends 2 month old son Mon-Fri 6am-4pm, and I just started training last night on a new job doing data-entry from home. My schedule will be Sat & Sun mid-afternoons, and I can pick up any other hours when they are available. Am I insane??? Possibly. Do I miss that stuff called sleep? Does a cat have an ass? Both answers are the same, YES!!! Although I love having the baby, I'm praying that his mommy can find a job at night. I know she misses him and would love to spend more time with him. I feel guilty everyday that I have him because I know how hard it is to leave them so young.