Tiger Haven's website gives you a lot of info as to what is involved. As many have said, you will need several "angels" who can constantly provide the needed funds. You will need to read and learn a LOT about each species.

http://www.tigerhaven.org/index.asp

You won't be able to "mix" other wild animals, and "any animal that needs help" as the knowledge base is too broad.

None in RI as I don't think we permit it. Read the Tiger Haven site, as there are plenty of regs in place in their state. If you do this in the north / northeast, you add a huge expense re heat in winter. The big cats are predominantly warm climate dwellers. They also talk about this at Tiger Haven.