Dogwalker.com can help you find dog walking opportunities, and Care.com offers resources for pet sitting and related efforts. DogVacay is a prime website for dog boarding–participants set their rates and make up to $200 a week.
If you enjoy children, I can't stress this gig enough. Get silly! Some childlike enthusiasm never hurt anyone, especially when stressed out with adult troubles like finances. Interacting with happy children can help put things in perspective.