I've been known for rescuing a bit. The hardest one for me was ALL the baby turtles as there was too often little chance or the time to rehabilitate them before they passed away. Most were just too far gone by the time someone brought them to me and there was a constant flood of them.
Also have worked with some other various reptiles, rats and other rodents and small animals, exotics and dogs of course. For the exotics I also used to do educational programs and speak at schools and other public events about the animals, conservation and keeping exotics as 'pets'.
The paperwork to become legit non-profit can be a trial but if it's something you find yourself doing often and a gaggle of rescues you are trying to care for the tax deductible donations are not just helpful but often necessary for continuing. Rescuing and caring for animals is not cheap by any means.