Unfortunately with some animals, opting to have the surgery may cause the animal more pain than it is already in. When our six year old golden retriever was diagnose with cancer, we were given the option of putting her through a pricey surgery along with weekly treatments that were $100 a shot. We knew this would only help us in the long run by prolonging our goodbyes. We kept her alive while she was still able to eat, drink, and move comfortably, but when the time came, we had to put her down.
Sometimes dogs get problems young and it's painful to let go, but if they cannot afford the operation and/or the outlook is not good, they should perhaps look into having the dog euthanized. Hip dysplasia can be very painful and I know after surgery the dog will most likely need some sort of PT.
Tell them to look into the care credit as Cara mentioned, but I don't really think people will be very willing to donate money for someone else's pet when everyone here has pets of their own to care for. They may also want to look for a vet that will take payments. That may be an easier option.