When we take a dog in, we have two programs:
First program*preferred*: you foster the dog to keep the dog from having too many changes before adoption, and you get to bring your dog to adoption events, we market the dog online for you to our many rehoming sites as our foster and we take care of the rehoming process for you to ensure best-fit adoptions;
Second program: we keep it in our home with our family and pets with already approved fosters (or we find a foster) - we require a rehoming FEE for this since we have to find a foster home, supply food, training, and so on. Whether it takes weeks or months to find it a home, we keep the dog with us and incur the cost of it's care and vetting.
Rescue is partially funded by our adoption fees, but this typically does not cover all of our expenses even in the rehoming program.