I want to.... eventually. I did volunteer at the Saskatoon zoo for a number of years.
The main qualifications are PAID experience (volunteering is good, but you will lose out to any candidates that have paid exp) and a degree in zoology or biology. You can get away without the degree if you have a lot of experience, but volunteer exp generally isn't enough to make up for a lack of schooling.
And yes, wages will suck.... generally starting at minimum wage for a lot of hard work (unless you get in at a large facility - where they generally hire only those with a lot of exp or long-term volunteers).
various cornsnakes, 0.1 black pine snake, 1.0 uromastyx geyri, etc.
"The only thing worse than a human who had no respect for other animals was a human who assumed all other animals thought and felt just like he did." --Julia Ecklar, "ReGenesis"