In terms of starting a wildlife centre you would need enough land and money to make sure you care for your animals. If you are planning to keep any dangerous animals listed under the DWA such as big cats you would need a Dangerous Animals Licence.
http://www.defra.gov.uk/wildlife-pets/wildlife/protect/dwaa/index.htm
If you plan to open a centre to the public for more then 3 days a year and charge admission you would be classed as a zoo and need a Zoo License. To get this you have to apply in advance as well as notify your local community of your intentions.
http://www.defra.gov.uk/wildlife-pets/zoos/licensing-act.htm
These are just two of the key points, there is a lot of work and legislation involved in running these centres. See Defras website in general for more information.
www.defra.gov.uk
You would need a lot of background knowledge and experience in caring for a range of animals, a good local vet and be willing to dedicate your life to these animals. If you are serious about this though look at doing a course in Conservation, Countryside Management or Animal Behaviour. I would more recommend however that you aim to work in a centre rather then opening a new one. A lot of these centres will take you on doing work experience or volunteer work and then consider moving you up to a full time job. They can also give you better advice on local colleges providing suitable courses. Good luck.
