I've worked at a zoo part time for 5 years. I currently work in the Education department doing presentations and behind scene tours, and most of my gigs are overnight/night tours...so I get paid to sleep :), free dinner and breakfast, and I get my weekend days off. 1-2 sleepovers per week = 16-32 hours. It's a non profit so the pay sucks...I probably only make about $5-7k per year. But it's fun, easy, and fulfilling work.
I also rent out a portion of a property I own. After expenses, I keep about $5k/ year.
I would love to work in environmental conservation full time, or at least part time (as a replacement for my full time job, which is working from home as a medical bill processor). I have to get more rental properties to be able to afford to go back to school for a science degree (if I want a zoo-keeping position), and to afford working a low-wage, competitive job.