If someone wants to open a wildlife rehab center, how do they make their money for operating costs?

My mother ran a wildlife rehabilitation center in South Florida for 20 years or so.

She pestered all the local big businesses, got discounts from grocery stores, pet supply and livestock supply stores. She was the science teacher at the church elementary school, so she got donations from church members. She also had a donation basket for when people brought critters in.

She used people who needed to work off community service for much of the carpentry and yard work required.

She and her partner worked very long, very hard days. She worked her retired husband from before sunup to after sundown, they never broke even. It has to be a labor of love.