a basic knowledge of animal husbandry would be favourable in most cases. i have a BTEC National Diploma in animal care, which means i am in theory qualified to manage an animal collection i.e pet shop, kennels etc, but there are also NVQs available which concentrate more on the basics and are more 'hands-on' than a diploma which involves a lot of written work.
But i think that if your friend has a genuine passion for animals, is unafraid of hard work and doesn't mind getting their hands dirty, then he/she is already qualified! :-)