Brutus's surgery for Cancer

Brutus was diagnosed with bone cancer(osteosarcoma) back in February. We've been back and forth between vet visits, oncologist appointments, and surgery consults. In this time frame his mass has gone from a golf ball size to a softball size. His CT's came back negative for metastasis in the lungs but the bone shows high risk for fracture.  We are opting to amputate his leg at this time before it fractures or gets worse. I have already come out of pocket about $4,500 so far. The estimate for the amputation surgery and post-op care is around $6,200 not including the chemotherapy he will have to go through afterwards. Unfortunately they want all of the money upfront no payment plans. Any help is greatly appreciated!